Jump to content

detective 21

triger cub swingarm clearence

Recommended Posts

Here's the problem, I have a what appears to be a feked off part-widened and lengthen swing arm and a 4x18 tyre on my rear wheel, to get the chain to run straight and clear the shock (already spaced slightly out) by a millimetre, the tyre has to be moved on to the left giving very limited clearance on that side and the wheel does not sit centrally in the swingarm. This does not seem right to me but I have nothing  to compare it against.

To me it seems that the swingarm is not wide enough, and maybe the sub frame is to narrow causing the shock interference.

Has anyone else experienced these issue, am I just missing something?

Share this post


Link to post
Share on other sites

Detective 21

I'm not sure if I'm reading your problem right but have you moved the engine over with spacers on the engine mounts?  also I use a spacer behind the rear sprocket (an old sprocket with the teeth machined off) it seems to work for me. Thats assuming you have the right "offset in the rear wheel when it was laced to the new rim.

Hope this helps, perhaps someone with specific knowledge will advise you better.

Share this post


Link to post
Share on other sites

the engine is spaced and the rear sprocket, the rear wheel offset is unknown as it is only a new bike to me not a new build, what should the rim offset be in relation to the hub? also though if the rim is moved to the sprocket side to put it in the middle of the swingarm the tyre would be in contact with the chain, then if I spaced the sprocket and engine more the chain would run through the rear shock

Edited by detective 21

Share this post


Link to post
Share on other sites

I know there is not a lot of clearance between the tyre and chain on bike that is in use but the swinging arm is of unknown origin I bought another hub and found it to be wider than the one in use Have just been the workshop where the other frame has an SM Produce rear an fitted the unbuilt hub brake plate and the spaced sprocket misses the frame and shock My engine is mounted as they can and I use a dished type gear box sprocket  

Share this post


Link to post
Share on other sites

Does the rear wheel fit into the swing arm on its own, with adequate clearance either side. You will always have on some bikes the situation where the tyre moves about on low pressure and rubs on the chain guard and the swing arm, exhaust and anything else within about 5mm of the tyre wall/tread. Try building the back of the bike with the drive side damper and spring assembly left off. The opposite side should support the weight, but I would replace the drive side suspension with a piece of solid bar or tube to hold the swing arm level, no twisting. Align the chain to the gearbox by placing a good straight edge or piece of angle iron or tubing alongside the rear sprocket (no chain fitted) you may find that the rear wheel spindle and hub may need the spacers modifying to achieve this. You will also need to check the alignment of the rear wheel to the front, do this with a pair of good straight tubes, I have used ( believe it or not) fluorescent lighting tubes with care....they do work as straight edges....I digress...sorry. Now you have some solid data to go on rather than uncertainties. You say that you have spaced the suspension unit on the drive side by 1mm and this is a tiny amount, you may have to go to 3-5mm. If you don’t grasp the wheel alignment ( no slight on your skill levels) google should help. Now you have straight wheels and hopefully an aligned drive chain. If the wheels are in alignment but the chain isn’t then consider moving the engine about in the frame with washers or spacers, another way is to space the gearbox sprocket with shims to move the sprocket in or out if feasible, I haven’t seen any pictures of the bike so this last mod may not be possible. The rear wheel rim should be central in the swing arm, if it isn’t then the offset needs tweaking, slacken the spokes on the side that is too far over, tighten the spokes on the other side to pull the rim over to the central position in the swing arm. You will need to get the rim re set by a wheel builder or someone who has the technique, possibly you. The last thing that I would consider doing after the initial data gathering is to remove a piece of the swing arm pivot point and fit it in the opposite side temporarily. By moving the swing arm across the frame slightly example 3mm may just give you the clearance you need.

I hope that this helps you to arrive at a workable solution. It sounds like a lot of work ( measure twice and cut once ) but in reality an hour should see you in a position to be able to sort the problem. 🙂

Share this post


Link to post
Share on other sites

As above,  I worked from the front wheel being central in the forks and aligned the rear from it. my offset if it helps is 66mm approx from centre of rim to face of brake drum with no brake plate fitted.

Share this post


Link to post
Share on other sites
On 8/10/2018 at 10:14 PM, naichuff said:

I know there is not a lot of clearance between the tyre and chain on bike that is in use but the swinging arm is of unknown origin I bought another hub and found it to be wider than the one in use Have just been the workshop where the other frame has an SM Produce rear an fitted the unbuilt hub brake plate and the spaced sprocket misses the frame and shock My engine is mounted as they can and I use a dished type gear box sprocket  

Feked Parts bought SM Products out. Anything formerly Sammy Miller made & sold is now sold by Feked.

Share this post


Link to post
Share on other sites

Yes I deal with Feked  as I have one complete Cub and one partly built cub I use to make and modify parts so they fit the good Cub

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×