Jetting after RB head mod

[BryanMcc]

I had Ron adjust my squish, it was almost 2.4mm, he took it back to around 1mm, my question is with the new squish setting will I likely new to rejet to leaner or richer settings? And is one circuit more affected the the other?

[Simmo737]

If its just squish and the stock compression ratio has been maintained, jetting should be the same, if you have had an increase in compression as well you will need to richen you main jet, and possibly but not definitely the needle notch.

I had this advice given by jd jetting, so I'd take it as accurate.

Cheers.

I'd call r b to ascertain exactly what was done.

[BryanMcc]

Originally Posted by Simmo737

If its just squish and the stock compression ratio has been maintained, jetting should be the same, if you have had an increase in compression as well you will need to richen you main jet, and possibly but not definitely the needle notch.

I had this advice given by jd jetting, so I'd take it as accurate.

Cheers.

I'd call r b to ascertain exactly what was done.

His email said compression bumped up slightly and squish reduced to .042, so richer for more compression huh, ok I wonder how many sizes I should go up as a starting point

[AZRickD]

I didn't go any richer after my RB head mod.

[Simmo737]

I'd try I step richer on the main jet, then see how it goes with a plug chop

[Jakobi]

How about the increased efficiency created by that massive reduction in squish height? Do you think that would mean you could put less fuel in there as whats going in is now being used?

But as stated increases in compression generally like a bit more fuel charge..

You might find it wants a touch more fuel, or a touch less. If it was close before I'd start there and adjust as you feel neccessary. You WILL find that any changes you make are much less erratic, and you'll really be able to dial in the circuits without it feeling like the jetting changes every time the weather does.

[BryanMcc]

Originally Posted by Jakobi

How about the increased efficiency created by that massive reduction in squish height? Do you think that would mean you could put less fuel in there as whats going in is now being used?

But as stated increases in compression generally like a bit more fuel charge..

You might find it wants a touch more fuel, or a touch less. If it was close before I'd start there and adjust as you feel neccessary. You WILL find that any changes you make are much less erratic, and you'll really be able to dial in the circuits without it feeling like the jetting changes every time the weather does.

Well...I guess I will ride it as is for a few min and then do a plug chop. Before this thing was super picky with jetting...I still have a hard time with plug chops as I don't really feel like I understand the art of the plug chop. I know how to do them just not really what to look for on the plug. I know the color I'm looking for just not where I should be reading it from. Thanks for all the replies for the jetting help!

[Jakobi]

I know exactly where you're coming from. My 2010 300 came with 1.3mm of base gaskets timing the piston flush with exh port at bdc. The squish was 2.6mm! The bike was horrible to jet and so sensitive to changes that it was almost impossible to accurately evaluate the jetting itself. You'd get it perfect one day and the next ride it would be off. Once I brought the squish to 1.25mm you can actually feel the bike go from rich, to just right, to leanish, and the whole time the bike still feels ridable. When its right it sticks. When changing a half a clip position you can actually tell if its better or not. The plug colouring will come up better with a cleaner burn as well. Basically with a huge squish clearance only so much of the fuel in there is getting pushed under the spark plug, some gets trapped under the squish band, the end result is inconsistant combustion. I'm pretty sure its part of the equation why the idles are so up and down on stock bikes too.

Just start her up and you'll know immediately that you've just spent the best money you can on your 2T.

[BryanMcc]

Originally Posted by Jakobi

I know exactly where you're coming from. My 2010 300 came with 1.3mm of base gaskets timing the piston flush with exh port at bdc. The squish was 2.6mm! The bike was horrible to jet and so sensitive to changes that it was almost impossible to accurately evaluate the jetting itself. You'd get it perfect one day and the next ride it would be off. Once I brought the squish to 1.25mm you can actually feel the bike go from rich, to just right, to leanish, and the whole time the bike still feels ridable. When its right it sticks. When changing a half a clip position you can actually tell if its better or not. The plug colouring will come up better with a cleaner burn as well. Basically with a huge squish clearance only so much of the fuel in there is getting pushed under the spark plug, some gets trapped under the squish band, the end result is inconsistant combustion. I'm pretty sure its part of the equation why the idles are so up and down on stock bikes too.

Just start her up and you'll know immediately that you've just spent the best money you can on your 2T.

Now your getting me excited to ride it! I never thought of the inconsistent idle being a result of a large squish, makes sense tho when you think of it. My husky wr300 has an idle like that, 2000 feet will take it from barely running to a somewhat fast idle, although the air screw in that bike ( as1) seems to actually work, where as the airscrew on the GG seemed to not change things much. Lots of people seem to set the squish at like 1.3 or 1.4, Ron set mine at .042 or just a very small tick over 1, what with the difference between 1 and 1.3 be and why choose one over the other? I did tell Ron I'm running 3700 feet and up which I'm sure is why he added a little compression, just didnt know if it had much to do with squish.

[Jakobi]

The less squish clearance the better. As an engine runs though the conrod actually stretches a bit just before it changes direction. You need clearance, because when the piston starts to hit the head its not so good. Ron has done enough heads that I'd trust his figures without a doubt.

You'll love it when you take her out for a ride! Enjoy!