New Cam Chain Won't fit

[denisducati750]

I'm putting the top end back together in my first engine rebuild attempt. Ordered new cam chain but it is one link too short. The engine is a '74 XS650 from the US and has a 447 on the block. I understand that there are two cam chains for this model depending on where in the world the bike was headed - the chains have a different 'pitch'. The key is apparently whether the bike is a '447' type. The old chain has DID219FT on it and the new chain has FTS219 on it. The supplier reckons the new chain is the right chain for the job, but even after removing one of the cam bearings to get the chain on the top sprocket, there is no way I can get the bearing back on and the the chain in place - just far too tight. The supplier said that if this didn't work then I had another problem - I've counted the sprocket teeth on the top sprocket and there are 36 which is I understand is correct. Have inspected the cam chain on the bottom sprocket through oil cover removal, and it's not sitting on a tooth or kinked. Any suggestions welcome. thanks, Slug.

 

[arcticXS]

It could be that the grease in your new chain is making it a bit tight. Maybe you could heat it with a hot air gun making the grease flow and effectively making the chain a little bit longer. Also, the thickness of base and head gasket will have influence on the chain "tightness"

 

[denisducati750]

Thanks mate. It was doing my head in - no way there was enough give in the chain grease-wise, so I ended up putting the old chain back in - it fitted perfectly - I only replaced it because with new pistons, guides and a re-bore I thought it best to renew everything I could while she was in bits. But today wasn't to be my day. As I tried to fit the joiner link, one end of the chain fell down into the cases with the small ring spanned I'd attached to it following. I've got the chain out - but now need to find that spanner - and start again. Have already learnt a lot with this as I've always paid someone to rebuild in the past. It'll be worth it in the end and I'm close to having the engine finished so I can sort out the new frame engine, drive and exhaust routes.

 

[TwoManyXS1Bs]

Is your front camchain guide fitted flat to the front of the tunnel, or is it protruding rearward, pushing the chain rearward?

http://www.xs650.com/forum/showthread.php?t=45845

 

[denisducati750]

Yeah, the front cam chain guide protrudes a little bit into the heads. The bigger screw in nuts are the issue as their threaded part protrudes - it's got nowhere else to go. But I took the from cam chain guide off again for that reason before re-fitting the old chain and it seemed to make negligible difference. Slug.

 

[3andit]

I just had this exact problem and I did everything you said... What I ended up doing was laying the cam chain out on a plank and put a nail between the last link and then took a flat blade screwdriver and tapped it between each link and pried on each link and that helped a lot then the other thing I did was take the bearings out of the cam and then put the cam chain on then torqued down the head to squish the new gaskets and after that it allowed just barely enough room to slip the bearings back on the camshaft... I gently tapped them into their correct position.... May not be the proper way of doing it but it worked for me

 

[denisducati750]

Geez, that's interesting! And reassuring too - I reckon I've tried everything as a first time builder but naturally doubted myself. A retired bike racer who now builds and tunes race bikes for his son is doing a car repair job for my son. I dropped out Friday and told him and showed photo of what was going on with my can chain. He said no way it should be that tight - rather being over tight, it should have a tiny bit of slack so the tensioner comes into play even slightly. Made sense to me. Good luck with yours though and thanks for the feedback! Slug.

 

[3andit]

I agree! but the place I bought the chain from even told me it would appear to be too short but that is just because of the grease in the new chain and that after you fire it up and the chain warms and "breaks in" it will be perfect.... So I hope they are correct! The chain is extremely tight.

 

[nj1639]

On a cam with no advance rod, TCI ignition we're talking here, I use a beefy Phillips head screwdriver inserted into the cam where the advance rod would go and use that as a pry to lift the now chained cam up high enough to slip the bearings on. Of course slip the bearing on the screwdriver before inserting into the advance rod channel.

 

[3andit]

On a cam with no advance rod, TCI ignition we're talking here, I use a beefy Phillips head screwdriver inserted into the cam where the advance rod would go and use that as a pry to lift the now chained cam up high enough to slip the bearings on. Of course slip the bearing on the screwdriver before inserting into the advance rod channel.

Lol I did that too ! Have you run one of these new chains ? I'm curious how long did it take for the chain to get some slack in it? I can't even get my tensioner screwed in properly right now

 

[5twins]

I always loosely bolt the head down. The chain then mates up even with the bearings on the cam. You can use washers and 1/2" drive sockets for spacers on the studs but since this is the way I always do it now, I went ahead and cut special spacers the right size from an old handlebar. I fought with my first couple until I learned this trick. Now it's not something I even consider a problem any more. They fit right on.

 

[TwoManyXS1Bs]

Just an FYI. Here's a cross sectional view of late model camchain and tensioners:



And, one of 5twins pics showing the front guide's protruding barrel bolts.
(Bottom of picture)

 

[5twins]

That cross section nicely illustrates how the chain should pass through the base of the rear tensioner. If you somehow managed to feed it through in front of that base pin, it would come up too short.

I should also mention the two different cam chains. Yes, there were two used, but not on the same model just because it was going to different markets. The early '70-'73 "256" motors used one type, the later '74 and newer "447" motors used another. The chains were different pitches AND different lengths. The "256" chain was 102 links and had an 8mm (.315") pitch. The "447" chain was 106 links and had a 7.77mm (.306") pitch. Make sure you have a 106 link 7.77mm pitch chain. And if you think that's a tight fit, imagine what one 4 links shorter would be like, lol.

 

[denisducati750]

This has been very helpful guys. I'll check again that the new chain goes around that bottom base pin correctly - my new chain is 106 links and the engine a 447 so that info now clears things up instead of wondering whether I had the wrong chain. I have fitted new gaskets as well and the idea of tightening the studs a bit by putting temporary sleeves over them is a good one - here goes. Thanks for all the advice!

 

[5twins]

It really works. I fought with the chains before doing that. You need to pull all the parts and new gaskets down and together. As you're doing it, it may not seem like it's accomplishing much, but it really is.

 

[nj1639]

Gonna mention here to make sure the cam wheel is centered in the head and both sets of cam bearings are pressed inward, snug. Save ya some leaks on the cam end seals. How would I know?