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Post by 4ce on Oct 4, 2020 21:06:54 GMT 1
I`ve had a 370 top end conversion done to my 250LC.
Will I need to change the primary drive cog? It is marked 85.
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Post by Tobyjugs on Oct 4, 2020 21:12:32 GMT 1
Are you talking about the cog on the end of your crankshaft? or do you mean one of the sprockets?
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Post by 4ce on Oct 4, 2020 22:20:33 GMT 1
Yes, the one on the crank. I meant to put Primary drive.
It`s my age you know.
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Post by arrow on Oct 5, 2020 0:30:01 GMT 1
You can't change the amount of teeth on the crank gear without changing the amount of teeth on the clutch basket. The 250 and 350 run the same set up here. I'm 99% sure the gear box is the same, so the change must come from the final drive sprockets.
You could leave as is for the ultimate wheelie machine, or use the sprockets from the 350 bike.
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Post by Tobyjugs on Oct 5, 2020 8:45:23 GMT 1
Some people change the primary gears on their bike for straight cut versions and these can come in different ratios as a pair.
They are normally changed to help the engine last longer if used and abused. The standard primary gears have the teeth cut on angle, this causes a force to pull or push the crankshaft sideways, which can cause the crankshaft to lengthen as it is only pressed together.
If you are going to bimble around like most of us do then this will be not worth the cost. How ever if you are going to rake the tits off it, the primaries will help the longevity of the crank.
There are two numbers written on the primary gears they should add up to 155 plus or minus one
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Post by 4ce on Oct 5, 2020 10:11:31 GMT 1
Ok, Thanks for the advice. I think I will leave as is. One thing crossed off the list that hasn`t cost me.  |
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