Sprocket and Clutch

Racing K Models

Re: Sprocket and Clutch

Postby Rubone » Sun Oct 30, 2022 8:16 pm

DaveAus wrote:Hi,

I’m still working away on getting my KR on the track and I’ve moved onto the clutch area.

My aim is to use the bike as a road racer and at the moment it has a 25t engine sprocket. I was wondering what the recommendation is for ideal size.

Also the clutch basket cover has holes drilled around it so oil can get into into the clutch basket. I was wondering if I’m better off buying a new cover and running a dry clutch or is the current set up ok.

Thanks
David

Dave, what rear wheel are you running as that is an important part of the equation. Factory KR, KRTT with drum, Aftermarket QD, rim diameter, etc....
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Re: Sprocket and Clutch

Postby Ferrous_Head » Sun Oct 30, 2022 8:55 pm

Dry clutches hold more power. They can get away with lighter (stock) clutch springs. If you choose to go with a wet clutch you might be tempted to use the 20% stronger (Barnett) clutch springs. These will play havoc with your clutch worm arms. bend them like pretzels.

The KR's were goof for 140+ MPH at Daytona. This is where wind resistance plays havoc with your clutch. Once you get over 100MPH it becomes a big factor. Changes everything.

After years of experimenting with organic, kevlar,asbestos and anything else I could find I took Steve Smnith's advice and installed sintered iron plates. Now I can run stock springs (lighter clutch pull) with no slip. Ever. Set the stack height at 35mm and spacing as per FSM.

The 25T engine sprocket is too small.
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Re: Sprocket and Clutch

Postby Ferrous_Head » Mon Oct 31, 2022 12:37 am

Just dawns on my. You might have the 5 plate clutch in there ?

I might have an alloy clutch shell cover if you do.
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Re: Sprocket and Clutch

Postby DaveAus » Mon Oct 31, 2022 3:45 am

Thanks for all the input.

Robbie - the rims are after market 18" and I've had 2 hubs welded together so I can run the brake on the left side and sprocket on the right. Ive got a range of sprockets from 40 through to 44 tooth.

I've just had a look at the transmission sprocket and its a 24 tooth. A friend who races KR's has suggested a 34t on the engine and a 19t on the trans and a dry clutch.

Here's a few pics of what I've got

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Re: Sprocket and Clutch

Postby Ferrous_Head » Mon Oct 31, 2022 6:58 pm

That gearing (with the 44) will put you in the ball park, probably around 115-117, depends on your tire size and max RPM you can use.

Under 100 mph a fairing is just a PITA.

Above 100 mph there is a dramatic difference between faired and unfaired bikes. A full fairing on my Ducati Singles added around 10 mph to the top end. If tou want to be serious about winning on the faster tracks you really need to do it.
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Re: Sprocket and Clutch

Postby DaveAus » Tue Jan 10, 2023 4:39 am

So for the time being I’m going to run a 30t motor sprocket.

The one on it was a 25 and the primary chain was 90 links. The 90 link chain was too small for the 30t sprocket and I’m trying to work out how many links I’ll need for the 30t.

Seems I can get a 94 and 96 link Sportster chains.

Thanks Dave
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Re: Sprocket and Clutch

Postby wz507 » Tue Jan 10, 2023 8:32 am

Consumer K, KH, KHK models with 30T engine sprocket used a 92T triplex chain. Here’s a link to a very reasonably priced one.

https://www.billscustomcycles.com/k-mod ... n-40005-52
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Re: Sprocket and Clutch

Postby panic » Tue Jan 10, 2023 11:58 am

Why do you suppose that H-D make such a very large assortment of internals ratios?
To accommodate individual tracks, not for top speed (controlled by the overall ratio and rear wheel OD), but for when & where to shift.
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Re: Sprocket and Clutch

Postby DaveAus » Fri Jan 20, 2023 3:26 am

wz507 wrote:Consumer K, KH, KHK models with 30T engine sprocket used a 92T triplex chain. Here’s a link to a very reasonably priced one.

https://www.billscustomcycles.com/k-mod ... n-40005-52


Thanks for the advice and link. Parts ordered.

Cheers
David
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