Jakobi
Super Moderator
I'm guessing you've been there.. How was it?
S3 Race 250 Port Matched Cylinder and Head
- Thread starter Jakobi
- Start date
I'm guessing you've been there.. How was it?
Jakobi
Super Moderator
I have been in dscussions with Dave (dmcca) who will be doing my head modifications. He has since signed up with this forum and will no doubt have some info to post into this thread himself. Hopefully some nice pictures as the work comes together.
So far we've decided that I will install the piston, and cylinder with the piston set with the exhaust ports at BDC. I will then take squish measurements (solder method), and calculate the trapped volue (sealing rings with grease and cc'ing with metho up to the bottom of the spark plug hole).
After this I will be sending the entire S3 cylinder and head (and insert that gives the tightest squish) to Dave to work his magic. He has a nice workshop set up and in particular is building a database for the software he uses to simulate effects on engine behaviour prior to modification. He will be taking measurements of the S3 cylinder and will be able to provide feedback how it compares to the standard cylinder and if any port changes have been made (other than cleaning up casting). So far he has taken measurements for a 2010 EC300R (NSE.ONE) and an EC250 (was this yours Lonetree? - AHH ROBKTM dbw). By running sims he will then determine the best gasket stack to meet my desired goals and then machine to spec. He also agrees with F5 (tighter is better) so we'll see what he does. The insert will also be corrected for volume to achieve whatever CR I want.
We confirmed the head and insert will both require the same amount machined off them to make sure that they seal, which will make the other 2 inserts redundant. If anyone with a S3 head wants them shoot a PM.
Dave has been really great to deal with and explains everything in nice simple terms. He's located in Australia (at the other end of the country from me) and seems to be building his business up nicely. If anyone else is thinking about going this route I wouldn't hesitate to recommend him based on my experience, or the feedback received by others who've had his work.
One last thing from Dave re the 250 he worked on: "I also mapped out the stock ignition curve and the dual map switch simply changes the entire curve by 2-3 degrees. I advanced the base timing by 2-3 degrees so that the 'wet' curve is now the same as the old 'dry' curve, and the new 'dry' curve has a little more oomph down low but still revs out fine." I may consider doing this to my bike also as I have never run the wet curve, even in the wettest conditions as a 300.
So far we've decided that I will install the piston, and cylinder with the piston set with the exhaust ports at BDC. I will then take squish measurements (solder method), and calculate the trapped volue (sealing rings with grease and cc'ing with metho up to the bottom of the spark plug hole).
After this I will be sending the entire S3 cylinder and head (and insert that gives the tightest squish) to Dave to work his magic. He has a nice workshop set up and in particular is building a database for the software he uses to simulate effects on engine behaviour prior to modification. He will be taking measurements of the S3 cylinder and will be able to provide feedback how it compares to the standard cylinder and if any port changes have been made (other than cleaning up casting). So far he has taken measurements for a 2010 EC300R (NSE.ONE) and an EC250 (was this yours Lonetree? - AHH ROBKTM dbw). By running sims he will then determine the best gasket stack to meet my desired goals and then machine to spec. He also agrees with F5 (tighter is better) so we'll see what he does. The insert will also be corrected for volume to achieve whatever CR I want.
We confirmed the head and insert will both require the same amount machined off them to make sure that they seal, which will make the other 2 inserts redundant. If anyone with a S3 head wants them shoot a PM.
Dave has been really great to deal with and explains everything in nice simple terms. He's located in Australia (at the other end of the country from me) and seems to be building his business up nicely. If anyone else is thinking about going this route I wouldn't hesitate to recommend him based on my experience, or the feedback received by others who've had his work.
One last thing from Dave re the 250 he worked on: "I also mapped out the stock ignition curve and the dual map switch simply changes the entire curve by 2-3 degrees. I advanced the base timing by 2-3 degrees so that the 'wet' curve is now the same as the old 'dry' curve, and the new 'dry' curve has a little more oomph down low but still revs out fine." I may consider doing this to my bike also as I have never run the wet curve, even in the wettest conditions as a 300.
(F5)
Gold Level Site Supporter
A simple 3 deg delay? That is pretty lazy. I'd assumed they had programmed several curves & tried them in difficult situations. . . because it works so well. Either way I like the wet function & use it probably 50% of the time, like yesterday when there was some tricky sections & unseasonable wet, but obviously our rainfall is far more than Auss.
I know 2 people with ISDE models which seem to be more aggressive power delivery. Both are experienced good riders & both leave them on the wet setting.
As far as the base setting goes you may have to test to find out. I fitted a road tyre to my 200 & dyno'd it. Often running higher comp one needs to retard ign a touch. Running high comp, close squish on 1/2 Av gas & 1/2 pump gas I found that std position worked best for this older no-switch ign.
You may find with new setup that it can't take more advance without detonation. Or you may find stock setting was pretty safe so as to cope with a multitude of crap gases one might encounter so more advance may be the ticket for your bike & gas. Maybe.
My point it test test test. If you care that much about 1/10ths. The 300 has all the power I ever ask for, and occasionally a tickle more than I wanted, but that's just my inner Muppet.
I know 2 people with ISDE models which seem to be more aggressive power delivery. Both are experienced good riders & both leave them on the wet setting.
As far as the base setting goes you may have to test to find out. I fitted a road tyre to my 200 & dyno'd it. Often running higher comp one needs to retard ign a touch. Running high comp, close squish on 1/2 Av gas & 1/2 pump gas I found that std position worked best for this older no-switch ign.
You may find with new setup that it can't take more advance without detonation. Or you may find stock setting was pretty safe so as to cope with a multitude of crap gases one might encounter so more advance may be the ticket for your bike & gas. Maybe.
My point it test test test. If you care that much about 1/10ths. The 300 has all the power I ever ask for, and occasionally a tickle more than I wanted, but that's just my inner Muppet.
Jakobi
Super Moderator
Few considerations here. I'll probably be running the same or even less compression than I am at the moment. I'll also be changing to a 250 so may be looking for some more oomph (maybe). Ultimately I'm not looking at sacrificing reliability in the chase of more power.
Don't know how much rain you've had over there lately but we have experienced a somewhat late season or as you'd call unseasonable wet too! Mud mud and more mud out. Ran it in sunshine all day long! I must admit that putting it on the pipe in these conditions is a waste of time and momentum is ones best friend.
The good news is that the arrangements with dmcca are falling into place nicely re the 250 work. I will be having him attend to the 300 head at some point too! All the suspension parts are starting to arrive, and I'm getting the extra hours up on the 300. It should only be a few weeks and there'll be some more progression with this thread.
Don't know how much rain you've had over there lately but we have experienced a somewhat late season or as you'd call unseasonable wet too! Mud mud and more mud out. Ran it in sunshine all day long! I must admit that putting it on the pipe in these conditions is a waste of time and momentum is ones best friend.
The good news is that the arrangements with dmcca are falling into place nicely re the 250 work. I will be having him attend to the 300 head at some point too! All the suspension parts are starting to arrive, and I'm getting the extra hours up on the 300. It should only be a few weeks and there'll be some more progression with this thread.
Jakobi
Super Moderator
Action time
Well the bike has close to 5000kms on it now (160hrs in total / 85hrs on current top end). I've got some time off work over Easter and the parts are all in the post for the rest of the bike so should be arriving over the next week or two. It feels like the right time to get a start on this change over.
I've spoke to Dave (dmcca) again and got his postal address sorted and informed him of the plans so all is well on that front.
I've still got to get some 2mm resin/rosin core solder as I can't be bothered twisting it up like I did last time and feel it will be quicker and easier this way. Hope to give the bike a thorough wash down Monday (stripped back to make sure the frame is clean). If time allows I might pop the pipe, drop the oil, drain the coolant and generally just get the bike ready for Tuesday.
I'm dedicating this whole day to taking measurements both of the 300 top end and the 250, and by the end of the day hope to have the 250 top end specced and ready to post by wednesday morning.
I'm hoping the C-clipper arrives so I can avoid the head aches when fitting the piston. Just out of curiosity, as I'll be just snugging everything up to set the port timing, get a squish reading on the head, and CC the trapped volume, do you think it would be safe to just slide the pin in without the clips? The bike will then be pulled back down again straight away. Or is there a big risk the pin will slide out and cause issues? Looking for feedback again
Thanks!
Well the bike has close to 5000kms on it now (160hrs in total / 85hrs on current top end). I've got some time off work over Easter and the parts are all in the post for the rest of the bike so should be arriving over the next week or two. It feels like the right time to get a start on this change over.
I've spoke to Dave (dmcca) again and got his postal address sorted and informed him of the plans so all is well on that front.
I've still got to get some 2mm resin/rosin core solder as I can't be bothered twisting it up like I did last time and feel it will be quicker and easier this way. Hope to give the bike a thorough wash down Monday (stripped back to make sure the frame is clean). If time allows I might pop the pipe, drop the oil, drain the coolant and generally just get the bike ready for Tuesday.
I'm dedicating this whole day to taking measurements both of the 300 top end and the 250, and by the end of the day hope to have the 250 top end specced and ready to post by wednesday morning.
I'm hoping the C-clipper arrives so I can avoid the head aches when fitting the piston. Just out of curiosity, as I'll be just snugging everything up to set the port timing, get a squish reading on the head, and CC the trapped volume, do you think it would be safe to just slide the pin in without the clips? The bike will then be pulled back down again straight away. Or is there a big risk the pin will slide out and cause issues? Looking for feedback again
Thanks!
Fred1956
New member
Just out of curiosity, as I'll be just snugging everything up to set the port timing, get a squish reading on the head, and CC the trapped volume, do you think it would be safe to just slide the pin in without the clips? The bike will then be pulled back down again straight away. Or is there a big risk the pin will slide out and cause issues? Looking for feedback again
Thanks!
Lack of clips for measuring everything should cause no issues- just don't get busy and forget to install them before start up !!
Jakobi
Super Moderator
Thats what I was thinking Fred. It'll be going on to measure the squish and then the trapped volume and then the head and cylinder will both be coming off and sent off. I'll need to clean the grease from the rings and ringland anyway so probably easier to take the complete piston right off again anyway
Getting excited!
Getting excited!
Jakobi
Super Moderator
Well its been a long day and I've been reminded why I'm not a mechanic! No issues faced. Just a lot of back and forwards measure this measure that.
I managed to measure up the current setup I was running (Stock 300 cyl, S3 Head, 1.3mm base gasket stack). It seems my squish was even larger than I remembered measuring it at last time. I did several measurements and settled on 1.95mm. The trapped volume was 23cc. Both top and bottom ring gaps measured in at 0.55mm. The piston has been warm enough to lightly glaze some oil on the underside of the dome. The top burn pattern is as expected from running a big squish (ie all over the shop). There were only a few areas where the carbon had built up and most was just a light oily coating that wiped off without much effort. I will post some pics later.
For the S3 cylinder, it appeared to be very much the same as the stock for the port locations. The casting is much cleaner as my stock has quite a lot of slop in one side on the transfers. Both cyldinders required a 1.3mm gasket stack to set the port timing, piston top flush with the exhaust port at bottom dead center.
The 250 top end with the ports timed as above and the S3 head with the black insert measured up very similar to the 300. Squish at 2.05mm. Trapped volume 16cc (however I was getting a bit mentally tired and ready for a beverage by then so it could be out by a mm. I did measure twice but still not certain so will get Dave to crunch the numbers for this one just to be safe).
After quickly doing a few numbers it seems the black insert boosts the compression ratio up big time on the 250.
S3 EC300: (23+293)/23 = CR 13.7:1
S3 EC250: (16+249)/16 = CR 16.5:1
Even if I missed a cc or two the 250 would still have a CR of 15.6:1/14.8:1
Note: Identified errors with viewing the fluid level at the base of the plug. Trapped volumes incorrect. Updates further ahead.
Pics coming soon.
I managed to measure up the current setup I was running (Stock 300 cyl, S3 Head, 1.3mm base gasket stack). It seems my squish was even larger than I remembered measuring it at last time. I did several measurements and settled on 1.95mm. The trapped volume was 23cc. Both top and bottom ring gaps measured in at 0.55mm. The piston has been warm enough to lightly glaze some oil on the underside of the dome. The top burn pattern is as expected from running a big squish (ie all over the shop). There were only a few areas where the carbon had built up and most was just a light oily coating that wiped off without much effort. I will post some pics later.
For the S3 cylinder, it appeared to be very much the same as the stock for the port locations. The casting is much cleaner as my stock has quite a lot of slop in one side on the transfers. Both cyldinders required a 1.3mm gasket stack to set the port timing, piston top flush with the exhaust port at bottom dead center.
The 250 top end with the ports timed as above and the S3 head with the black insert measured up very similar to the 300. Squish at 2.05mm. Trapped volume 16cc (however I was getting a bit mentally tired and ready for a beverage by then so it could be out by a mm. I did measure twice but still not certain so will get Dave to crunch the numbers for this one just to be safe).
After quickly doing a few numbers it seems the black insert boosts the compression ratio up big time on the 250.
S3 EC300: (23+293)/23 = CR 13.7:1
S3 EC250: (16+249)/16 = CR 16.5:1
Even if I missed a cc or two the 250 would still have a CR of 15.6:1/14.8:1
Note: Identified errors with viewing the fluid level at the base of the plug. Trapped volumes incorrect. Updates further ahead.
Pics coming soon.
Last edited:
Jakobi
Super Moderator
Piston and head look ok I guess. I've run a bit lean at some point as there is oil build up on the underside of the piston. Not black or carbon, but definite heating of the oil to leave residue like you see on the side ports of the piston. There is a small carbon mark in the middle. I've run so many different combinations of needles, clip positions, and mains it could have happened at any time however I think the 172 main I've run for the last 2 rides could be the cause. I had a small black mark in the middle only of my last piston too which I knew I ran really lean on the needle on one instance. It didn't have this same glazed effect though. Just a neat black dot. Could also be the change from GRO to Amsoil. Never the less, it'll be back to the drawing board looking for new base lines when putting it back together as a 250.
A bit of carbon build up on the head exhaust port side. And some carbon build up on the dome of the piston. Bringing the squish band in should help to cool the piston as it will assist in flowing the fuel across its dome towards the center. At the moment its like it just burns whereever it is.
A bit of carbon build up on the head exhaust port side. And some carbon build up on the dome of the piston. Bringing the squish band in should help to cool the piston as it will assist in flowing the fuel across its dome towards the center. At the moment its like it just burns whereever it is.
Jakobi
Super Moderator
And the last couple. I didn't take any pics of the S3 cylinder of head installed as they were only snugged down to take some squish measurements and cc the trapped volume. I was getting a bit tired by that point and looking towards just getting it done so I can pack it all up to be shipped off tomorrow.
GMP
Active member
Jake,
Those comp ratios are not correct, you are not allowing for the exhaust port(s). The calculated theoretical comp ratio should use the swept volume of the cylinder from the edge of the PV flap to the top of the stroke, not the full displacement of 249 or 293 cc. This is not the right way to do it anyway as compression changes (lowers) with PV opening and there are some leakage losses at kickover speed. Thats why it should all be based on cylinder pressure using a good guage. The guy doing the head work should adjust the volume of the dome(compression) as the final step based on your fuel and original head volume (that he should do accurately with a burette/pipette and glass plate).
I never had a piston come out of a bike without some golden brown glaze under the dome, its normal.
Those comp ratios are not correct, you are not allowing for the exhaust port(s). The calculated theoretical comp ratio should use the swept volume of the cylinder from the edge of the PV flap to the top of the stroke, not the full displacement of 249 or 293 cc. This is not the right way to do it anyway as compression changes (lowers) with PV opening and there are some leakage losses at kickover speed. Thats why it should all be based on cylinder pressure using a good guage. The guy doing the head work should adjust the volume of the dome(compression) as the final step based on your fuel and original head volume (that he should do accurately with a burette/pipette and glass plate).
I never had a piston come out of a bike without some golden brown glaze under the dome, its normal.
Jakobi
Super Moderator
Thanks for the info Glenn,
I realise the numbers I crunched are only for an uncorrected compression ratio. Its a quick and easy calculation only. To work out the corrected compression ratio which will be a much lower number there are many more variables to take into account.
Dave has had his hands on a few gassers now and is building up data which he uses to do simulations. I will be sending the entire cylinder and head to him with the info I have provided here. He will then take further measurements and then let the software do all the work as to determine the best setup. With any luck we'll get him chiming in here and posting some more graphs to demonstrate the effects of raising compression, altering port timing, etc.
I really appreciate the input and am enjoying learning more about how these things work. Glad to hear the glazing under the piston is not a huge concern. This is only my 2nd time in a 2 stroke and both on the Gasser. Every time I pick up a tool its a new lesson waiting to be learnt.
I realise the numbers I crunched are only for an uncorrected compression ratio. Its a quick and easy calculation only. To work out the corrected compression ratio which will be a much lower number there are many more variables to take into account.
Dave has had his hands on a few gassers now and is building up data which he uses to do simulations. I will be sending the entire cylinder and head to him with the info I have provided here. He will then take further measurements and then let the software do all the work as to determine the best setup. With any luck we'll get him chiming in here and posting some more graphs to demonstrate the effects of raising compression, altering port timing, etc.
I really appreciate the input and am enjoying learning more about how these things work. Glad to hear the glazing under the piston is not a huge concern. This is only my 2nd time in a 2 stroke and both on the Gasser. Every time I pick up a tool its a new lesson waiting to be learnt.
(F5)
Gold Level Site Supporter
Duck me fays! Those CRs seem high! My 300 measures at 12.6 I think standard setup. 16.5 is higher than I run in my race 50 with Av gas!!! Is it a methanol head
, or how is it measured?
One has to be careful to get the engine upright without air pockets & I go to 2 threads up the spark hole to account for the plug. I use a light oil like 5W fork oil.
I'd argue that a gauge is only useful for gauging wear, not effective compression. I've measurably increased compression and ended up reading the same on a newish German comp gauge. OK it was a high compression, but it illustrates the issue.
Besides when you start the bike dynamic compression is quite different due to pipe action, that's why I don't buy the whole ex port 'corrected' thing.
Now I'm not saying that you can't have a situation that off pipe the compression is effectively higher with the PV down, but I still don't buy that 2 strokes are measured one way & 4 strokes another despite the cams overlapping into compression stroke. When you have an effective pipe on a competition 2 stroke engine, compression ratio will guide you to maximum you can safely run with a given fuel.
, or how is it measured?One has to be careful to get the engine upright without air pockets & I go to 2 threads up the spark hole to account for the plug. I use a light oil like 5W fork oil.
I'd argue that a gauge is only useful for gauging wear, not effective compression. I've measurably increased compression and ended up reading the same on a newish German comp gauge. OK it was a high compression, but it illustrates the issue.
Besides when you start the bike dynamic compression is quite different due to pipe action, that's why I don't buy the whole ex port 'corrected' thing.
Now I'm not saying that you can't have a situation that off pipe the compression is effectively higher with the PV down, but I still don't buy that 2 strokes are measured one way & 4 strokes another despite the cams overlapping into compression stroke. When you have an effective pipe on a competition 2 stroke engine, compression ratio will guide you to maximum you can safely run with a given fuel.
Jakobi
Super Moderator
I thought the same thing with the CR for the 250 aswell. Very high but then they do label the black insert as "high high".
To measure I used metho and a 12cc syringe. A slight smear of grease to help the rings seal and then top dead center (locked in place at the flywheel). I did both the S3 300 and S3 250 both with a gasket stack of 1.3mm and both had the ports timed the same with this setup. Once I hit the bottom of the threads (which was hard to see - had a little torch to shine some light in to help) I then continued to fill to the top of the plug hole as a reference. Both took 5ml to fill the plug hole to the very top threads (28ml and 21ml respectively).
Today I measured the piston dome heights to also pass onto Dave to assist in calculating the trapped volume for comparison against my measurements. The 300 came in at 3.3mm where the 250 runs a 3.8mm.
To measure I used metho and a 12cc syringe. A slight smear of grease to help the rings seal and then top dead center (locked in place at the flywheel). I did both the S3 300 and S3 250 both with a gasket stack of 1.3mm and both had the ports timed the same with this setup. Once I hit the bottom of the threads (which was hard to see - had a little torch to shine some light in to help) I then continued to fill to the top of the plug hole as a reference. Both took 5ml to fill the plug hole to the very top threads (28ml and 21ml respectively).
Today I measured the piston dome heights to also pass onto Dave to assist in calculating the trapped volume for comparison against my measurements. The 300 came in at 3.3mm where the 250 runs a 3.8mm.
(F5)
Gold Level Site Supporter
it still seems about 2-3 points too high even for crazy octane gas. I had to lift the front wheel up 1/2M to get the engine level. Then I measure as many times as it takes to get a consistent reading with cleaning in between. I'm used to doing small cc cylinders where tiny changes mean large ratio differences. Even so the 300 took bleeding ages as it was sat in the bike & makes it hard to see.
Jakobi
Super Moderator
You make some very valid points F5 and in all honesty I wouldn't be surprised if there is some error on my part (especially on the 250) as I was getting a bit mentally fatigued by late in the afternoon. It'll be very interesting to see what figures dmcca comes up with when he calculates it. He advised he should be able to get pretty close by cc'ing the combustion chamber and using its volume in conjuction with the piston dome height and the squish readings I sent him. I'd be more inclined to trust his figures than my measurements. As they say, experience comes with practice and thats what it was for me.
In hindsight I should have done as you suggested and taken a few different readings. Ie triple checking my work.
In hindsight I should have done as you suggested and taken a few different readings. Ie triple checking my work.
