clutch gearing running a jacketshaft on kt yamaha engine

[fasteddie14]

i will be gear 21-57 on engine , I think 53-54 on rear alxe running 1/5 dirt track

 

[Jake3890]

i will be gear 21-57 on engine , I think 53-54 on rear alxe running 1/5 dirt track

In my opinion I think you will need a bigger then 53 rear gear but the 21/57 is common belt drive ratios

 

[spincycle]

21/57 on primary (belt drive to crankshaft) and on the secondary side I would probably be on a 22-23 on the clutch and about a 65 on the rear sprocket, you could run the 53-54 on the sprocket but you're gonna need to be pretty small on the clutch driver gear....could end up getting gear bound or over revving it tho....

 

[flattop1]

I would start with a 16 .
Or what spin suggests .
Somewhere around a 3.40 ratio.

 

[flattop1]

So a 2.95 or 3.40 . Probably better to go 2.9 less chance of gear bound / over rev .
Pipe or can ?

 

[spincycle]

Never had an opportunity to run a 2 stroke on a 1/5th mile, but more than likely, your not going to be off the throttle much getting in or through the corners, with like 16/54 on the secondary side with 21/57 on the primary side, not for 100% sure, but I would tend to think you might run out of motor pull (gear bound) before the end of the straightaway, which is gonna mess up your corner entry...etc, etc, etc....jmo

 

[spincycle]

16/54= 3.375 and 21/57= 2.71
3.375 x 2.71= 9.16 final drive ratio
9.16 is gonna create high motor rpms...quickly....maybe too quickly...I'd be inclined to try this combo on a small indoor oval if I was running a kt....

 

[Jim46]

are you sure you want a 9.00 , I think I was running a 9.00 on a 1/8 ,

 

[flattop1]

Been there. Definitely better to start out geared higher .
A 18 would be close to the 22/65.
8.14 vs 8.02

 

[spincycle]

are you sure you want a 9.00 , I think I was running a 9.00 on a 1/8 ,

8.30 - 8.40 is what I normally started with on an 1/8th, and down to 8.00-8.10 if it started biting up at all...and it was turning about 14,500..

 

[Jim46]

thats why I was saying a 9.0 for an 1/5 . Maybe a 6.0 off the hip ,

 

[DD83]

thats why I was saying a 9.0 for an 1/5 . Maybe a 6.0 off the hip ,

1/5 is a bigger track than a 1/8th I'd think you'd want to be down in the 7's on a 1/5th

 

[fasteddie14]

Sorry guys the track size is 1/3 mile, ben hur speedway jackshaft setup is new but been racing old gearing 9-76 with wet clutch back long time ago

 

[flattop1]

Well at least theres time too contemplate this .

 

[Jake3890]

Sorry guys the track size is 1/3 mile, ben hur speedway jackshaft setup is new but been racing old gearing 9-76 with wet clutch back long time ago

I race there with my Yamaha and I run a 21/57 belt driver and 22/65 on the clutch and rear

 

[CarlsonMotorsports]

I race there with my Yamaha and I run a 21/57 belt driver and 22/65 on the clutch and rear

Yea, that 8.02 sounds a lot closer to me. I would think you could even be on less gear and not twist the engine so hard - but tune and pipe determine where you really need to twist your 2cycle. We ran 9/72 back in the day and won plenty @Crawfordsville with our Yamahas - but that's when twisting them 14K and clutching 10.9K was leading edge.
Ben Hur is not really a 1/3 mile - you gear it more like a 1/4 mile track. I don't even think it was a 1/3 back when it had the dogleg. It's a big track, but gear it like 1/4 mile and you'll be fine.


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[fasteddie14]

What is a good range to run top rpms on Yamaha engine about 20 years old but still in good shape

 

[Jake3890]

What is a good range to run top rpms on Yamaha engine about 20 years old but still in good shape

I run mine at Ben hur 14600 at the end of the straightaway, and it held together just fine

 

[Jim46]

FYI Hortsman is making DXL parts again