New Cylinder on an Old Bike

[Millar]

Hi Guys, first post on here, I've been lurking for far too long. I ended up buying a 2006 ec300 about a year ago based on this forum and I've been loving how it feels over the xr600 I was riding before.

I've read that the older bikes were tuned to have more power in the lower rev range, sacrificing the top end compared to the later bikes, which I've noticed. I stupidly had a test ride on a 2013 ec300 and had it doing power wheelies in third gear which mine would never do! I definitely prefer the power delivery of the newer bikes!

Just wondering what it would take for my bike to run like a new one. Has anyone put a new cylinder from a later bike on a older bike and noticed the power characteristics change much? Is it only the cylinder that has changed over the years?

I've spent a lot a of time playing with the jetting and although it runs a lot better than when I bought it, it doesn't have the top end that the new bikes have. The bike is basically stock apart from the jetting. It still has the banana silencer an a uncut head. Machining the head is on my things to do list but I haven't got around to it yet...

I have been considering getting a new 300 and have the funds but if I can get mine to run like a new one it would probably last me another year or more.

 

[bowhunter007]

My '01 300 would loft the front tire as easily as any new(er) bike. I'd give her a good once over. Compression test, even teardown the top end, and take a peek inside. Do you know how many hours, on the top end? Anyway, that's where I'd start. However, if given the option...I'd have the new bike and pick away at the old one ' till she's right, or just sell outright.

 

[Cruiser]

And check to see if it has the reed spacer in it,, if so remove it for more power. That was there to tame it out.

 

[spooly]

And check to see if it has the reed spacer in it,, if so remove it for more power. That was there to tame it out.

can u explain more about this reed spacer??

 

[Millar]

My '01 300 would loft the front tire as easily as any new(er) bike. I'd give her a good once over. Compression test, even teardown the top end, and take a peek inside. Do you know how many hours, on the top end? Anyway, that's where I'd start. However, if given the option...I'd have the new bike and pick away at the old one ' till she's right, or just sell outright.

Thanks for the reply, I don't have any problem lifting the front wheel when I need to but I do have to put some work into it. My bike pulls really well low in the revs (as well as a new one) but really lacks in the top end. That's why I was thinking it might be due to changes in the cylinder design over the years. I put a new piston in it with a .5mm base gasket not long after I bought the bike and it did run a bit better. I've put about 80 hours on the current top end so it'll be due for another soon.

It's got good compression, PV moves as it should and the reed petals are in good condition. I'm struggling to think of anything else that might be taming the top end so much. The only thing that I haven't really checked is the timing, someone might have played with that I guess.

A new bike is very tempting at the moment but I'm thinking that there might be better things to spent the cash on like travel, I'm only 21.

And check to see if it has the reed spacer in it,, if so remove it for more power. That was there to tame it out.

I'll do this next I think. I was going take it out a while ago but there seems to be a lot of conflicting opinions on how it affects the power delivery.

 

[Millar]

can u explain more about this reed spacer??

From what I understand the reed spacer was put in the 300s to correct the the crankcase volume vs cylinder displacement ratio. From what I've read it seems that taking the spacer out can give a stronger top end but sacrifices a bit of torque at the bottom. I'll post back here when I take mine out but I won't be able to do it for a few weeks.

 

[spooly]

From what I understand the reed spacer was put in the 300s to correct the the crankcase volume vs cylinder displacement ratio. From what I've read it seems that taking the spacer out can give a stronger top end but sacrifices a bit of torque at the bottom. I'll post back here when I take mine out but I won't be able to do it for a few weeks.

Thanks. .it will be interesting to hear the results... me personally I wouldn't sacrifice bottom pull for top..

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[Zman]

I would measure your compressoin and then measure your cylinder head squish. I suspect having the head cut will make a world of difference for you. A cheap easy thing you can do right now is advance the ignition timing a few degrees. Be careful to listen for detonation (rattle like a can full of marbles). Depending on your funding for this project you may also want to have the cylinder ported as some of the cylinder castings were kind of rough.

 

[Neil E.]

The exhaust has to flow well, so make sure the muffler core is positioned correctly and the packing stays where it should.

 

[gassergrant]

My old GG goes like a stabbed rat, pops the wheel up in theird no problem, I don't know much about it but changing the port timing ie porting and polishing
Try carbon reeds remove the spacer which I did. I've put a full fmf system on too use good hight octain feul , like here in the uk we get 98 Ron use that. It's not as drutall as a Mx bike but has no probs keeping up on track

 

[Zman]

As I understand it, the factory manufacturing tolerances combined with safety factors on the engines resulted in some bikes having appropriate compression ratios and other having low compression. As a mfr, GG does not want to send an engine out the door with too high of compression that could result in a failure and warrantee claim resulting from use gasoline having the octane rating specified in the manual. My 2000 XC300 had low compression from the factory resulting from excessive piston to head clearance.

 

[Jakobi]

Even comparing my 2 engines (2010 EC250 with S3 Racing Cylinder, machined head to 1.25mm 14:1UCCR and 2013 stock cylinder, machined head to 1.25mm 13.1:1UCCR) they both make very different power. Both running 13:50 gearing. The newer one is a top end beast that seems to rev further and harder. It also vibrates a lot more in the mid range. The older has a stronger pull off idle and into the mid but falls short up top.

Granted both are running different jetting specs too. They won't run the same on the same jetting bike for bike. It may be the carb, or maybe the engines. Who knows. The old one had a trued crank and vibes much less through the bars.

Both bikes however will loft the front very very easily in 5th gear in the meat of their power curves. Even in 6th if played right. 3rd gear you need to watch out or you'll take a trip over the back.

 

[n_green]

And then the '14 engine delivers (and jets) differently again. Pulls like a freight train off the bottom (easily as good or better then my '11) and screams up top. '14 motor is best of both worlds IMO.

 

[Jakobi]

And then the '14 engine delivers (and jets) differently again. Pulls like a freight train off the bottom (easily as good or better then my '11) and screams up top. '14 motor is best of both worlds IMO.

I think my 250 and your 300 will jet pretty similar once we're dialled. I've been using 40 NEDW#2 175 and the mid to top end is great, feels a bit buzzy at 1/4 throttle and think it could use a bit more fuel, but I don't want to go any richer down low. I'm already at AS2 and everythings about perfect. Easy starting, smooth pull. Going in 1/4 turn on the AS it blubbers up. I'm thinking I'll drop a NECJ#3 in and leave the 40 pilot. The richer clip position should keep things similar around 1/8th, a bit richer at 1/4 throttle to 1/2, and little change to the top end. Might give me more meat down low too.

 

[n_green]

I think my 250 and your 300 will jet pretty similar once we're dialled. I've been using 40 NEDW#2 175 and the mid to top end is great, feels a bit buzzy at 1/4 throttle and think it could use a bit more fuel, but I don't want to go any richer down low. I'm already at AS2 and everythings about perfect. Easy starting, smooth pull. Going in 1/4 turn on the AS it blubbers up. I'm thinking I'll drop a NECJ#3 in and leave the 40 pilot. The richer clip position should keep things similar around 1/8th, a bit richer at 1/4 throttle to 1/2, and little change to the top end. Might give me more meat down low too.

My jetting will be very close to yours when dialled. I have been running 42 NEDW#2 172. AS 1.5. Pre head mod running .5mm base gasket it was as close to perfect as I've ever had a two stroke. With the exception of a light burble at 1/8 throttle which pretty much went away under load it was great everywhere. Was also only using 8l/100ks.
Now with the modded head (1.28mm squish using a .3mm base gasket - NFI re new CR) and riding in similar temps/elevations/humidity however different part of the state (surely that doesn't make a difference) I found it to be reasonably rich right off the bottom through to 1/4 throttle, where from then on it was still perfect. Admittedly I didn't fiddle with the AS, it could easily have come out to 2 as the idle was very low and stalling a lot and it was loading up slightly in tight single with low throttle openings.
I'm also thinking of throwing in the NECJ#3 to try and clear up the bottom without affecting the mid and top.

Anyway, sorry for hijack OP. A new bike is great, but my advice would be to spend a small amount of $ getting your current bike great and the rest of your $ travelling. Get a new bike in a few more years when they have reliable DI and you don't have to worry about jetting as per my above post

 

[Millar]

Bit of an update for those interested. Today I decided to machine the head and am quite happy with the result! I really should have put a new piston in the bike before cutting the head but at the moment I'm not really sure how long I'll keep the bike for so I avoided the expense.

I basically followed F5's thread so thanks for that mate! Very helpful

My initial squish was 2.3mm, not sure on the original compression ratio, should have checked!

I made a spark plug mandrel from an old spark plug and with a bit of persuasion from a big hammer I was able to get the axial and radial run-out down to about 1 thou, close enough for me! I started by machining the squish band at about 11 degrees to match the piston and then took about 2.5mm off the face the bolts to the top of the cylinder to bring the squish down to about 1mm at the cylinder wall and 1.1mm at the inside edge of the squish band.

I took the flywheel off so the piston would sit a TDC. I then measured the clearance volume with a large syringe and 2T oil, which ended up at 19ml. I was aiming for about 25ml for a compression ratio of 12.7:1 so I had to remove 6cc of material. I did this freehand using a tool with a radius ginded on the end, not perfect but good enough.

Bolted it all back together in no time and had a quick test ride in the dark. The bike's running a lot better now and the only thing that it cost me was a days work! Way more low and mid range power with some improvement up high! I'll need to play with the jetting a bit more to get the most out of it. The idle hangs a bit after a hard run but I should be able to fix that on the air screw. What are people's thoughts on the piston wash? Maybe a bit lean?

Next thing to do is to get it jetted a bit better and then remove the reed spacer.

 

[Zman]

I was going to cut my own head too, but when I chucked up my head with a sparkplug it was way out, I did not think of the hammer alignment option.

 

[Millar]

I did try it first with just a normal spark plug but it was miles away from being true so I held the head in the lathe backwards, holding onto the very outside of the head, to machine the spark plug round and perfectly centered to the head. Ideally you'd weld a big lump of round bar (40mm+ diameter) to the spark plug, put the spark plug in the head and the head in chuck jaws and then machine the round bar so it was centered to the head but I didn't bother. The spark plug machined round had about 10 thou run out before adjustment, there just wasn't enough meat to hold it in the jaws perfectly true, that's were the hammer came in.

 

[celler]

My 2005 was flat on top with the stock fmf pipe. I replaced it with the fmf fatty and it reved much better. My 2011 is still better but the 2 are similar


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