Exhaust pipes

[florence]

Please can anyone tell me, will CB650 exhaust down-pipes fit onto a CB500 four?  My exhaust is falling apart, the MOT is due fairly soon and I need to find a very cheap way of repairing it.(the gun-gum only lasts for so long! and the holes are getting bigger)  

I have noticed there are some CB650 down-pipes on ebay but I don't want to buy them if they can't fit.

The down-pipes on these bikes are a real mud-trap, the bikes on it's third set now.  I think I should put a rubber flap at the bottom of the front mudguard.

[Bryanj]

There was some talking about this on the US site and i think the end opinion was no as the exit angles are different, but i didnt linkit and cant be 100%

[florence]

ahh, sorry don't often go to the US site anymore.  I will have a look.

[Spitfire]

When I bought my CB750 F1 new one of the first things that I did was to fit a mudflap to the front mudguard to save the downpipes. Unfortunately this did not work as 28 years later the pipes did rot, not where the crap from the front wheel went but on the welded joints, oh and the front mudguard under the flap rusted, this again too about 28 years to become an issue !

Cheers

Den

[matthewmosse]

Rubber flap behind mudgaurd is deffinately a good idea, it helps a fair bit. depending on how bad the corrosion is welding can outlast gun gum, re making a collector box area isn't totally beyond home fabricators. Even easyer if you have a supplier of thinwall pipe - most exhaust suppliers apparently can sell you some if nothing suitable is forthcomming from their skip.

[florence]

Spitfire, those were the original pipes, these are Motad pipes which I suspect do not have such a good layer of chrome and we do get a lot of mud around here which I am far to lazy to kick off.   Even so, they have lasted for ten years so I do see what you mean.

Matthewmosse, good idea, I could weld some pipe onto the good bits of the down-tube.  I am getting ideas of some dreadful Frankenstein pipework which will look awful but be functional and I'm liking it already.  I did see a picture of a brilliant cb550 which had a home-made exhaust and I was very impressed, although I suspect it was too loud to be of use really.

[matthewmosse]

Yea gods, that's horrific! bet you'd be pulled over in 5 minutes cos it's Very obviously not standard. If it looks semi normal then you'll probably get away with some manky loud pipes, best I had was bsa rocket 3 silencer (70's raygun type - now quite rare) that had been welded onto a bsm system whose silencer had rusted - I swear the thing amplified the engine noise. I heard the seller delivering the outfit a clear 6 miles from my home, yet the bike was never stopped by the old bill in the 100, 000 miles it was set up like that. If you're up for welding things a good bet would be to trawl a local bike breakers for any 4 cylinder system the right diameter in the headers dept and adjust the inlet angle with some carefull cutting and welding. That is if nothing better suited turns up on evilbay and new is too costly.

[florence]

good idea, I only included that [picture as a joke, i would never put anything like that on my bike. 

I like your idea of adapting another system.  I don't know how hard it would be to line up though.  Sometimes even the proper ones can be difficult.  I will keep looking out for something and in the meantime, more gun-gum.  Motads have gone up to about

[SteveD CB500K0]

If you have the facilities (and the skill), you could buy an old Motad and cut off the headers. Then either make your own can or adapt an eBay bargain.

Like this:



The can is homemade.

[florence]

Very nice job Steve, I have thought about that or my preferred and latest idea is to get two down-pipes for each side and make up a 4/2 system.

[lordwhimsey]

If you have the facilities (and the skill), you could buy an old Motad and cut off the headers. Then either make your own can or adapt an eBay bargain.

Like this:



The can is homemade.

How hard was that to do Steve? I've got a ratty old Motad and the silencers been hacksawed off at the point your end can joins. I'd like to attach one of those short megaphone silencers that you see on eBay; is this a welding job?

[SteveD CB500K0]

This was done by the PO.

His site is here.

[lordwhimsey]

Thanks Steve. I've just had a new plan! I'm going to see if it's possible to do this with the Motad headers:



This is from Andy's build thread on the US forum http://forums.sohc4.net/index.php?topic=57836.msg640544#msg640544

[SteveD CB500K0]

That might be tricky as the Motad has the four headers meeting just under the brake pedal in a square form. To fit two cans onto that would probably require some custom fab work.

[lordwhimsey]

I was thinking of doing away with the joiny bit (technical term) all together and making a four into four.