Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: billdn on May 13, 2017, 07:13:57 PM
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can anyone explain installing the cam shaft on a 400/4. the engine is out of the frame and being reassembled on the bench. the Haynes manual procedure just will not work as the cam shaft will not go all the way through the sprocket with the chain on. it is a new linkless chain. a you tube clip i saw said to hold up chain, slide camshaft through and then slide on sprocket and put chain over - easy peasy i thought! however there just doesn't seem to be enough slack in the chain to get it over. i now have the camshaft half in and half out and the chain is so tight i'm afraid i'll break or stretch it. i've removed the cam guides front and rear to give a bit more room but to no avail. the flange on the shaft that the sprocket fits on fouls the bearing seat as well. any ideas. the chain was from David Silver so i guess should be the right length. Any ideas before i resort to the club hammer. Totally wrong but just feels satisfying! >:(
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I've just done mine about an hour ago so I know what you're on about.
Make sure you remove the rear slipper top holder thingy - the one that's secured with two M6 bolts towards the rear of the head. This will give you enough length inthe camchain to fit it properly.
Hope this helps.
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Have a look at instructional clip...
https://m.youtube.com/watch?v=YACuV9E3f7w
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Thanks for the reply Mike, but alas to say I've already removed that as well. :( it just seems that the chain is about 3-4 links too short. i can rotate the engine with the bolt on the points end of the crank and the chain moves ok. i'll try the video link you suggest.
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Yep , that was the video clip i watched earlier in the week which filled me with such hope! i notice he mentions jiggery pokery with the cam chain - sounds like the bottom end of the chain may not be on correctly. So all i need to do is get out the half wedged in camshaft and try again.!!!!! :-\
any other ideas that come to mind would be great. i'm trying to persuade the chain off the sprocket but it doesn't have enough slack to even do that. the cam shaft is in to the point that all i need is the flange, that the sprocket bolts into, to get past the last bearing journal and it's home - although its 2 -3 mm bigger than the gap available.
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I would check the amount of links. I few months ago I had a 500 four cam chain that would not go on the sprocket, I started to doubt myself as I build engines all day long. The chain on the 500 is 88 links but, this fresh out of the box chain only had 84 when the box had 88 clearly printed.
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That's a bastard - having to strip down the engine because of a dodgy camchain. It's worth checking though. I would put a tippex mark on a link and start counting. I presume you've still got the old one for comparison.
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Well I've counted the links or more precisely the side plates that join the links, an old cam chain gives 41 and the one fitted has 41 too.the old chain wasn't fitted but was bought as part of a job lot of 400/4 bits so i assume was a chain for this model. (i know assume nothing!) but all the other bits are so i feel fairly confident it is. i then ensured the head was fully torqued down. the cam sprocket has 32 teeth and matches the other spare sprockets i have in width and hole positions. the cam shaft is the same as the other spare camshafts (all marked R5- if that means anything.) i have taken some photos of the offending article and as can be seen it won't go in BUT won't come out either. i'm considering cutting the sprocket off but shards of metal dropping in the internals fill me with dread. any thoughts would be appreciated.
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In your second image, it looks like the hole in the centre of the sprocket, obviously the one the cam shaft fits through, is not a circle but oval. Is it possible to hold the shaft while you rotate the engine to get the higher part of the hole uppermost and thereby giving you more play?
Peter.
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I know I had issues fitting my cam after a topend rebuild,although this is a 500,
I had to unmount the chain from the cam sprocket ,and rest the cam in the bearings,the center hole in the sprocket is eccentric,,so
it can allow enough slack in the chain to then engage the chain,and fit to the cam,
sorry I can't completely remember how I did it,
hope this helps
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Wish it was Peter , it's just a naff angle and my poor photographic skills. unfortunately it is round :-\
John - i thought i might try that but there doesn't even seem to be enough slack to persuade it off the sprocket - unless you have a nifty trick. i have tried it. my thoughts would be take off the chain, remove head and have a look inside - if i could just get that b****y chain of.! >:(
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i'm considering cutting the sprocket off but shards of metal dropping in the internals fill me with dread. any thoughts would be appreciated.
Would it not be easier to split the chain ?
Edit....my thought is based entirely on Women's logic by the way !!!!
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Can you take the chain off the sprocket, then lay the camshaft into it's bearings with the sprocket fitted into the undercut next to sprocket boss, then wind the chain onto the sprocket and finally slip the sprocket onto its boss.
I think that's how I did mine.
Dave.
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Front chain guide removed will give more room I think.
I ended up removing the rear slipper blade temporarily, being careful that the small location damper it sits in did not come out of the tensioner horseshoe at the same time.
From memory the chain was off the sprocket when fitting the camshaft.
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The camshaft has got to be on the head bearings, the sprocket off the shoulder on the cam to fit the chain and then lifted onto the shoulder. To get the timing right it's got to come off the shoulder, moved on link by link until it's right then put back on the shoulder.
Hope this helps.
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Thanks for advice peeps! Finally got cam chain off -who says brute force doesn't work ! And proceeding to re install without the Haynes manual 🏍
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Haynes manuals are rubbish, they dont do anything the Honda way. They appear to just get any johnny that works on bikes to blow the engine apart then try to figure out how it goes back together. Try to remember that these were built on a mass production basis where things need to assemble easily, if your needing force your doing it wrong so dont carry on. As said previously, cam has to be on its bearings which requires sprocket to one side of cam and chain off the sprocket. Do it that way its dead easy. You could use your haynes manual for lighting the barbecue over the weekend. Download the genuine Honda manual off Ashimoto's dropbox link. Good luck.
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They can be "wrong" , it has been said :-\
Some of the Haynes books are ok especially the car ones which you can pick up for sod all on ebay !
Page 17 of the genuine Honda Shop Manual for the CB350-400F is very brief on camshaft installation so presumably there is another generic SOHC manual with photos and words to supplement this?
The disassembly instructions (p 13) do however instruct to remove the sprocket and chain then the chain from the sprocket, then pull the camshaft from the RHS.
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Haynes manuals are rubbish, they dont do anything the Honda way. They appear to just get any johnny that works on bikes to blow the engine apart then try to figure out how it goes back together. Try to remember that these were built on a mass production basis where things need to assemble easily, if your needing force your doing it wrong so dont carry on. As said previously, cam has to be on its bearings which requires sprocket to one side of cam and chain off the sprocket. Do it that way its dead easy. You could use your haynes manual for lighting the barbecue over the weekend. Download the genuine Honda manual off Ashimoto's dropbox link. Good luck.
Funny Roy because I think the old Haynes manuals are quite informative (rubbish modern ones though) and can be a nice supplement to the genuine Honda ones.. I built 2 400/4 engines using on the Haynes manual in the 1980's and several 250K engines and never had a problem with them. That included using them to work out the crank bearing codes for the 400/4 ..I then went to the local 5-star dealers and he just scratched his head and couldn't check my sums, so I just told him to order them , fitted them and they Plastigaged fine. The Honda manuals too have glaring errors if you check closely enough and they evidently had an army of Jap graduates queuing up to write the CB750 manuals.
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Thanks for advice - prized chain off and after removing head again found chain not on crank fully. After that plain sailing. :)