Mod GPX GYT Clutching and Jetting Help

2ooosrx

2ooosrx

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Oct 2, 2004
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Age
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Location
Gurnee, Illinois
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www.cbperformanceparts.com
Hey guys, we are throwing together a mod GPX GYT 433 sled to go after a guy in our circuit who continues to win every weekend. We have the engine all back together with the GYT pistons, cylinders, pipes, and we are going to run I believe 38 mm flat slides on the sled. We already made a spacer to allow us to run a convention yamaha secondary on there. We are going to try to run a polaris p-85 clutch too. I know alot of you out there are running this type of sled and I al just looking to get our tuning close. Any help with the jetting specs both pilot and main would help out alot. We are probably going to run filters on the sled. Also, where do we go in terms of clutching this beast? Spring, weights for the primary. And what do you recommend for the secondary setup. Any help would be greatly appreciated. Thank You

-Matt
 

MATT, I PM SOME STUFF TO YA. ANYWAYS BEST SET-UP IS BASISLY A COMET 102c , RUN A 78-79-80 SRX SECONDARY WITH STOCK SPRING WITH 340 SRX HELIX. JETTING YOUR GONNA HAVE TOO START HIGH AND WORK BACK. PRIMARY SPRING EITHER THE YELLOW GREEN OR PURPLE. WEIGHTS ALSO IS TRIAL AND ERROR. P-1, C, N-1, K-1. ALL NOTCHED FOR ENGAGEMENT. 3:16 (yammie tony)
 
Yes I know you sent me some stuff I am just looking for as much as possible to choose from so I will have less trial and error. Our biggest problem is that the first time we are actually going to test this sled out is in the first turn of our race. We really have no test time with it so it needs to be pretty close. Any one else have input for jetting or what not. Thanks
 
the polaris P85 is a far superior clutch than the 102c comet is. far more durable too.
as for jetting, test test test with throttle chops.
 
Give the chassis a lift by using a front skid arm only from a GP433. It offers better leverage. Use NEW rear springs from the GP as well – if you can’t find them wind up the stock ones with hockey stick wood on the post.

The stock carb and GYT clutch will work fine. You can’t guess with aftermarket – you will need to test. If you go with so sad stock carb and clutch – wind up the secondary as tight as you can.

We ran the engine stock GYT on pump gas. Shorten the head pipe 3/8"

We won a ton of races on that sled, back when there was 5 heats to make the final.
 

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From my limited exprience,the stock yammie secondary clutch doesn't seem to shift out fast enough.I'm going with a roller for my mod gpx one of these days.
And the pipe mod for the 433 is to cut 15 MM from the center section of the expansion chamber.
What circuit do you run at??
 
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The 77 srx clutch works really well if tuned right. Remember turning weight!!!! The best clutch I ever used was the three pole Reactor clutch. Gary knows his s%^t.
 
do you even cut the pipes if you are running the GYT pipes? We are just racing in a little circuit up in northern wisconsin. Probably close to 100 sleds that show up. The guy who continues to win the mod class here also races at eagle river and does fairly well.
 
hey Deano will an SRX secondary bolt right on to an Exciter? Thanks in advance.
 
i think i would go with yammiegods set up.he knows his stuff when it comes down to those ole yamahas.no sense in testing on race day.as for your carbs well i think your gonna have test,test,test.good luck
 
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