2011 GG 300 SD squish, comp, and jetting data
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Bikerdad450F
New member
the machining is done...
now to bolt the head back on and re-check the squish, maybe now a .095 " piece of solder will actually squish down for a good reading. I chucked the head up in a 4 jaw and cut .053" (1.34 mm) off of the mating surface, then lightly chamfered the holes, if the measurements happen to come out OK tomorrow, then I'll take it to get hard anodized. wish me luck.
now to bolt the head back on and re-check the squish, maybe now a .095 " piece of solder will actually squish down for a good reading. I chucked the head up in a 4 jaw and cut .053" (1.34 mm) off of the mating surface, then lightly chamfered the holes, if the measurements happen to come out OK tomorrow, then I'll take it to get hard anodized. wish me luck.
Jakobi
Super Moderator
now to bolt the head back on and re-check the squish, maybe now a .095 " piece of solder will actually squish down for a good reading. I chucked the head up in a 4 jaw and cut .053" (1.34 mm) off of the mating surface, then lightly chamfered the holes, if the measurements happen to come out OK tomorrow, then I'll take it to get hard anodized. wish me luck.
Good luck! Most will say just shaving the head down will increase compression too far though.. Hope it works for you.
GMP
Active member
My 250s have been set up in the high 190s with no problems on pump gas. This is not a lot of compression that would cause a lower end problem, and the bike still revs out very well.
Remember with squish clearance its all about consistancy across the band. A tight, more narrow band will be more effective than a wide band thats tight only on the outside edge. FWIW, Ron just highly polishes the combustion chambers of his modified heads. This has proven fine by me, as after close to 100 hrs on two different bikes all that was needed to clean the head was a wipe with a solvent rag. Clean jetting and Amsoil Dominator oil. Anodizing by nature is a rougher surface, and not neccessary anyway.
Remember with squish clearance its all about consistancy across the band. A tight, more narrow band will be more effective than a wide band thats tight only on the outside edge. FWIW, Ron just highly polishes the combustion chambers of his modified heads. This has proven fine by me, as after close to 100 hrs on two different bikes all that was needed to clean the head was a wipe with a solvent rag. Clean jetting and Amsoil Dominator oil. Anodizing by nature is a rougher surface, and not neccessary anyway.
Bikerdad450F
New member
cont... I bolted the head on this morning and squished some solder to 1.40 mm exactly. I removed the solder then did a cold compression test,(WOT, kill switch depressed, kick it till the gauge stops climbing) and got 175 psi, I'm happy with that so I'm going to get the head re-anodized, then move on to other areas like tuning the forks (they were at riders edge for re-valving, good price too.)
Skidad
New member
Oh crap that was a tease...hoping for a ride report
Gonna be like a different bike with the head mod and new suspension tweaks. Look forward to the next update.
Bikerdad450F
New member
No ride report till the forks come back, they are in transit. Perhaps monday or Tuesday June-27 or 28th. I am curious what other machining the DB mods include. As stated before. my 2009 EC300 had 2.74 mm of squish at the extreme outer edge of the piston, the measurement quickly tapers to a larger gap as you measure the squish band closer to the center. So if I read all of the info correctly, a minimum "squish band" to "piston top" clearance should be 1.2 mm and ideally between 1.2 and 1.6 mm. So all I did was go to the middle (Conservative, I thought) figure of 1.4mm squish. The bike pumps 175 psi cold now, up from 135 psi. I'm thinking that alone will do it for me, BUT the mystery to me is "what about thinning the I.D. of the squish band"? The engine would be losing compression as a result ofremoving some material from the combustion chamber and raising the CC figure. Wouldn't I be going backwards? Assuming that performance gains are to be had from having a narrow squish band, I assume I would have to re-machine the "gasket surfaces" as well as trim the band to size, in order to keep the 175 psi comp.
Is this sounding correct? I better do some web surfing on 2 stroke head mods. Has anyone heard about those slots that people are machining into there 4 stroke heads' squish zone?
Is this sounding correct? I better do some web surfing on 2 stroke head mods. Has anyone heard about those slots that people are machining into there 4 stroke heads' squish zone?
You're good at 175. What altitude, btw?
Shoot some oil in the cylinder and your compression will go up (some say that is the proper way). I was 175 dry at 1,300 MSL here in Phoenix.
Ron reshapes the combustion chamber for various reasons including making the charge compress to the center. I wouldn't bother with it
Shoot some oil in the cylinder and your compression will go up (some say that is the proper way). I was 175 dry at 1,300 MSL here in Phoenix.
Ron reshapes the combustion chamber for various reasons including making the charge compress to the center. I wouldn't bother with it
gasser
New member
Ron (RBD) has done both a 250 and a 300 head for me and the squish came out the same across the squish band. Those heads, like yours, had a tapered squish before Ron recut them. I am very happy with Ron's work - better running and better gas mileage.
Bikerdad450F
New member
Squish band
All great info. Thanks guys, that bit about flattening out the squish band is interesting, I have read elsewhere that the squish band (when set correctly) really aids in increasing turbulance in the cc, there is likely where your extra HP and milage come from but I'm not positive on this. I may run the engine how it is for now, and then do some more machining in the future, we'll see.
All great info. Thanks guys, that bit about flattening out the squish band is interesting, I have read elsewhere that the squish band (when set correctly) really aids in increasing turbulance in the cc, there is likely where your extra HP and milage come from but I'm not positive on this. I may run the engine how it is for now, and then do some more machining in the future, we'll see.
Bikerdad450F
New member
So when the squish band is measured, its possible that it will be tapered, and that we are taking our measurements from the outside edge which will read the smallest. This is where I plan to achieve 1.3-1.4mm..
Looking forward to the ride report
I don't know how many different styles of OEM head that Gasser uses for their 300's but so far it sounds like they have the taper in the squish band.
Has anyone ever tried grooving the squish band with 3 or 4 radial grooves, I hear claims that it increases milage, but I don't know first hand.
S3 head on the bike next week. Who wants to start machining custom inserts??Bikerdad: Are you referring to grooves like "Singh" grooves on a car head? I did some really cool work building a Ford 302 with a .030" squish, or quench as the car community calls it. The car got good mileage, and made serious torque!
I would be interested in getting the squish right, then experimenting with adding a groove or two from the edge of the combustion chamber to the center where the squish band blends into the bowl.
I would be interested in getting the squish right, then experimenting with adding a groove or two from the edge of the combustion chamber to the center where the squish band blends into the bowl.
(F5)
Gold Level Site Supporter
The important parameters are
1. the squish clearance (too big & you aren't effectively cooling the piston as well as could be & wasting the gas that never enters the CC).
2. The Compression ratio.
3. MSV. The max squish velocity. an engine will have a sweet spot (range) where combustion is best with the correct speed that the gas is squished promoting enough turbulence for complete as possible combustion. Tight squish clearance over too a large an area may produce too much turbulence. This can be tailored over this range to the type of power curve required in conjunction with the compression ratio.
Tapered squish reduce the MSV, but should be tapered opening toward the CC, not the other way around. Obviously manufacturing tols mean this & the clearance could be all over the place.
All these weird & wonderful grooves & lines appear to do is alter the MSV, but this could be done by other ways. I smell marketing. There are programs to estimate MSV.
Personally I find the 300 (I have an 07) enough of a step up from the 200 that now the jetting is sharp I want for no more power. However come piston time I can't help myself & will skim the head down to reduce the squish. I will however measure the volume & reduce the comm back down to std so I can kickstart it easily which I value more than any extra power on offer.
1. the squish clearance (too big & you aren't effectively cooling the piston as well as could be & wasting the gas that never enters the CC).
2. The Compression ratio.
3. MSV. The max squish velocity. an engine will have a sweet spot (range) where combustion is best with the correct speed that the gas is squished promoting enough turbulence for complete as possible combustion. Tight squish clearance over too a large an area may produce too much turbulence. This can be tailored over this range to the type of power curve required in conjunction with the compression ratio.
Tapered squish reduce the MSV, but should be tapered opening toward the CC, not the other way around. Obviously manufacturing tols mean this & the clearance could be all over the place.
All these weird & wonderful grooves & lines appear to do is alter the MSV, but this could be done by other ways. I smell marketing. There are programs to estimate MSV.
Personally I find the 300 (I have an 07) enough of a step up from the 200 that now the jetting is sharp I want for no more power. However come piston time I can't help myself & will skim the head down to reduce the squish. I will however measure the volume & reduce the comm back down to std so I can kickstart it easily which I value more than any extra power on offer.
Bikerdad450F
New member
I just bolted on the modified head with 1.4mm squish. and did a test pass or two on pavement. Yeah the bike is still fast but it is not jetted correctly. it was closer before the mod actually, but the temp today is 15 deg. warmer and humid too soooo, maybe some issues from that too. My point is, when I dial it in for best jetting, I'll post the results. and to answer your question, I did mean the "Singh" grooves.
mrkartoom
New member
Reviving an old thread here. Last season was a big loss for me and I never got around to sending my head and carb out to RB. I just got finished doing the measurements and started looking for old posts to get a good comparison of pre-mod readings. Thought I'd pass along my readings:
Squish (at outside edge): 2.37mm (.093in)
Compression: 148psi (cold/dry)
Never could get mine jetted the way I wanted to last season, so I'm anxious to bolt up the modded head and carb.
Squish (at outside edge): 2.37mm (.093in)
Compression: 148psi (cold/dry)
Never could get mine jetted the way I wanted to last season, so I'm anxious to bolt up the modded head and carb.
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