Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: adespin on June 24, 2018, 01:34:30 PM
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Has anyone had problems fitting new David Silver 341 exhaust system, I hit a problem fitting these on today, the outer pipe hits the rear brake pedal pivot on the top seam and will not pass it. The pipe is fully home in the exhaust port and lining up with the rear bolt. As it's Sunday i'm unable to query this with DS.
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Ade I’d suggest removing # 3 pipe, then refit # 4 on it's own and see if you can get the rear footrest hanger about through the pipe and in position. You may need to seeing / flex the pipe to get it under the rear brake pedal, but you should.have a few mm clearance once the home is in/pipe in position. They've a close/tight fit in this area but hopefully you should be fine..
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Not a hope in hell James, the silencer body is rubbing on the lever boss, on top of that i have now tried to fit 1 and 2 pipes, the rear hanger bolt is a very tight fit but probably could be persuaded with a mallet, but to my horror when i looked at the front view number 3 pipe is a couple of mil' from touching the filter body. I've now packed them up ready for shipment after i speak to David Silver tomorrow, i wonder what their responce will be.
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Don't take this the wrong way Ade, but I have a feeling this is partly due to the way you're attempting to fit these mate. Compared to Honda parts, the tolerance on those is way worse admittedly, but you do have a fair degree of movement to play with. You need to have all 4 crown/clamps in place to play around with angles/pipe position - a very small change in exit angle translates to a massive shift at the rear silencer.
Certainly looking at the angle of pipe #4 from the front you need to get that pipe much tighter to the frame to follow the correct line - I reckon you could get it to clear the pedal but without being there in person it’s difficult to say.
Anyway, sounds like you drawn a line under it which is probably sensible and have a go with a second set. Fingers crossed for you.
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Judging by the number of restorations you have completed, you have probably bought and fitted several sets of silencers, have you had this kind of problem, by that i mean you had to send them back, if so were there any quibbles.
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The repro HM341’s are way more of a struggle to fit than either genuine Honda pipes or the HM300’s from Yamiya.
Don't expect a simple slide on / perfect fit/alignment (sadly).
In my experience you have to really ’fight’ them into place.
Unfortunately they will be under tension initially, but after a few heat cycles they generally seem to adopt the new position.
Plenty of other forum members have fitted them so would be good to hear other opinions..
Anyone else care to chime in?
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Although not DSS 750 pipes, I bought a complete 400/4 system from DSS and it was an absolute pig to fit. The collector was hard pressed against the sump pan and I thought it was never going to fit but eventually and after taking it slowly and with some manipulation it fitted. I expect the 750 system is similar so keep trying.
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We have had serious struggles with DSS repro pipes, defo a 2 person job with plenty of swearing but got there in the end. Strange, because the CMSNL repro pipes are easier to fit but I thought they all came from the same manufacturer. Maybe DSS sells CMSNL's rejects.
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I agree with James they are a bugger to fit but again with a little patience (not my strong poont) and a bit of persuasion and willing they do go on. Make sure they are fully home on the flange at the head as I’ve found that makes a huge difference if one isn’t quite home
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Its a few years since I fitted a set of CSML repos to my K2 - they'e supposed to be from the same source from memory. I remember really struggling to get the rear mounts to line up but they did fit with much struggling and grumpyness
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I have DSS 341's on my K1 The same pipe is close to the oil filter as yours and they just clear the front engine mount bolts and just clear the brake peddle.
I have always struggled to get the two right hand pipes on until today when I realised my rear mount had been bent.
Ten minutes with a block of wood and scissor jack soon had the frame straight again and they now go on with ease.
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I have DSS 341's on my K1 The same pipe is close to the oil filter as yours and they just clear the front engine mount bolts and just clear the brake peddle.
I have always struggled to get the two right hand pipes on until today when I realised my rear mount had been bent.
Ten minutes with a block of wood and scissor jack soon had the frame straight again and they now go on with ease.
I have had that before, a bent rear foot peg right mount out by 4mm and the pipes on that side did not want to line up.
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I spoke to DS today, they are sending Fedex to pick up the pipes tomorrow, they said they will try them on their bike to test, and suggesting that the frame is possibly bent, but if that is the case then surely pipes number 1 and 3 would also not fit, but they go on ok, anyway time will tell, fingers crossed.
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If it is ok on the left and having problems on the right, may be rear foot peg hanger bent ;)
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There's no strength in the rear hanger at all it bent back easy.
I only realised it was bent as I thought I had better change the rear tyre and give the bike a Crick clean for next weekend.
I can now also confirm I have a small amount of rust starting on No1 pipe
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My friend's CB750 (1970, professionally restored before purchase) always exhibited problems when refitting the right hand silencers following maintenance. Eventually, someone noticed that the rear footrest mounting bracket on that side was around 1/4" out of alignment. We suspect that at some time in its long life, it had been down on the right hand side. There was also a small crack in the frame where the welded bracket was attached, revealed only after paint was removed.
It was straightened and the crack welded, no troubles after that with fitting the pipes!