extended swingarm ????

[fallguy666]

Would a 4" over swingarm make a 350x slower or feel like it tops out to quick? The reason I ask is because me a my buddy have identical '86 350x's and mine will smoke him.when we drag race he gets me off the line but I pull on him(hard) and pass him by third gear? Same exhaust(DG)same air filter,same jets.mine has a new top end but his has a nos motor.when we got his motor it still had the motor mounts bolted to it where they cut it out of the frame.my compression is 198,his is 176.I'm lost on this one as the only difference is the swinger?

[fallguy666]

Oh yeah,both have new stock sprockets and chains

[Yamaha_Rules69]

The length of the swingarm will have no effect on speed in a straight line. Do they both have the same tires? If so you guys should trade bikes and drag. Its probly more operator error, or a poorly adjusted/jetted machine. If you beat him on his, he is a slouch when it comes to drag racing.

[fallguy666]

Tried changing rides.same outcome.as far as jetting,they are both identical and the numerous plug chops say they are both spot on.I'm really confused on this one.his just feels like it runs out of gear sooner and quicker than mine? Both run a 13/40 setup

[fallguy666]

As for tires,his are old school turf tamers and mine are brand new bazooka's ( hole shot knock offs) both in 20-11-9

[Yamaha_Rules69]

Maybe his bike is spinning due to not enough traction, or his clutch may be slipping. There are a number of factors it could be. You should have put this in the this vs that section of the forum.

[fallguy666]

Um,no.its not a vs thread.lol.its a tech question.as far as spinning,no.he just flat takes off.the clutch is perfect.I would have felt it when I raced his.I'm stumped

[RIDE-RED 250r]

Valve adjustments??

Yours might be spot on and his may be due for an adjustment. Improper valve lash can have a significant effect on performance.

[fallguy666]

This could be the answer!!!! I checked the valves on his motor bout 8 months ago and they were perfect.it might have twelve hours on it since then,hard hours drag racing and wheelies.I will check and report back

[fallguy666]

He paid around $1800 for the motor less than a year ago.it was in an aqaintinces dealership for 20 something years

[Ol Deuce]

As for tires,his are old school turf tamers and mine are brand new bazooka's ( hole shot knock offs) both in 20-11-9
The difference is in the tires! even though they say 20x11-9 the diameter of the tires are different! I battle tire size all the time! Ol Deuce

[fallguy666]

We thought about that.we are within half an inch of each other.it even did this with my old wore out tires?

[NeverLift]

22 PSI lower than you motor translates to less HP add on the extra rotating mass of 8-10 inches of chain and that's slowing him down too. Have you ever weighed his tire/wheel combo compared to yours? I bet yours are lighter.

[fallguy666]

The difference could only be marginal.also I am 35#'s heavier than he is? We actually had my wife race me on his just to see.same outcome and she is only a buck ten

[atc007]

Do you know how much machine work thousands of guys over the years have done to GAIN 22 Lbs of compression lol!!!! Assuming all bearings and rotating mass/drag are the same. The compression and tires are the difference.

[RIDE-RED 250r]

Good call on the compression difference guys! I somehow missed that... That is significant for sure!

Just re-read the initial post...

Fallguy: You stated your engine has a fresh top end. If you are running a Wiseco piston, even the lower compression ratio Wiseco of the 2 piston profiles offered is still quite a jump in compression ratio over an OEM setup at 10.25:1. The higher comp ratio offered is 12:1....

Stock compression ratio for a 350x was 8:1 if I recall. If you used a Wiseco piston in your rebuild, there is your answer!

Both of my 2 brothers each have a 350x. Both have exhaust and K&N filters, jetted for those mods. One has the OEM piston still, the other has a Wiseco 10.25:1. And I can tell you from personal experience, that 10.25:1 piston is VERY noticeable in the seat of the pants compared to the trike still running the OEM piston.