new to me 1980 ltd help in set up for vintage drag racing please

[sxrsist]

hey all i am new to kawi group, my first love is yamaha but wanted to get something out of norm, we run a 79 exciter 440 and a 1981 srx in vintage drags, never see many kawis so picked this one up. ran a couple races last year and was ok but no where near what it should be. wondering where to start in jetting as someone before me put 38 mil mikunis on it. also what rpm should the shift point be at ? i paln on macining a yamaha seconday clutch for back drive so i have some tuning parts and a comet 102 up front. any help would be appreciated.be interesting if could make it keep with my 81. the exciter 440 would give it a run last year

[Teherr]

I have a 80 and 82 LTD and have 38's on both.  Both are recent builds and haven't fine tuned jetting.  With that said, I would start with 35 pilots, 290 mains, 2.5 slide, 6dh7 needle.   The 80 LTD has good potential. 

[sxrsist]

Thanks a lot.  At least a starting point.  Would you know where optimum rpm is to shift them at. Have a comet 102 on it so need to find weights  for it.  I know will need engagement to come out of any bog. Last year the one race we did do it just fell on its face after half track. I'm sure was going past it's power as it was running out around 8700 or bit higher. My guess is around that 8200 range but can't find any good day o sheets for them

[sprocket]

 The Aaen clutch book is a good read.

[sxrsist]

yes a very good read thanks but im not asking how to clutch im just wanting to know what rpm the power is being made.

[rminier]

 If yours is the 1980 LTD 4/6 that came from the factory with round slide Mikuni's....the STOCK engine was rated at 77 HP @ 8300 RPM....
taken from:       www.torysvintagesleds.com         website.

[sxrsist]

Not sure what stock carbs were on it. There 38 slide mimunis on it. Ow

[Interceptor398]

Stock carbs on the 4/6 are 36 econo jets marked 36/90 and idle RPM is set at 2500, unlike the Invader's that were set at an idle of 3000RPM.

[sxrsist]

So what would be opinion in drag racing.  Is the ltd much better then a regular invader ?   The ltd is a heavier sled for sure

[jimvw57]

The LTD is a heavier sled, dual exhaust and electric start (also heavier)they do have decent takeoff if the carbs are right and balanced, and the clutch is good.

The 340 is a light sled with plenty of torque, fast off the line but it does top out at around 80 mph.

[sprocket]

38mm carbs are good I ran 42mm on my tachometer (EGT brand) 1000 Rpms @ idle, I never idled mine @ 3,000 Rpms that was too high. The book that I have 1980 LTD 4/6 says  Engine RPM idle speed 2500rpms,  Engine RPM at full throttle 8300  duel exhaust mufflers,  Engine engagement approximately 4100 Rpms.  Dry weight approximately 430 pounds, 76hp the mono-head claims 77hp in stock form & thats 1981.  Depending on what you're reaching for speed or E.T.  It all depends on how you set your snowmobile up  there is 1000 different ways to reach your goal good luck

[sxrsist]

Thanks everyone.  So target rpm is 8200 to 8300.  Hope we can get the jetting down and make it rip

[sxrsist]

Ok running a comet 102c. Anyone have any secrets for weights and springs ? I have purple spring so comes out of the hole awesome.  But over revving so need to find a weight

[sprocket]

it's kind of hard to give anyone the exact numbers unless you have all the information that is needed everything changes too by the weight of the driver example your driver weighs 125 verses  a 200 pound person your snowmobile will react differently every time.

[sprocket]

Note
I could give you the perfect set up what I believe but then you go do it and it doesn't work that's why everybody says in racing test test test and more test I'm not trying to be a downer on what you want to reach I'm just stating the facts.