350 exhausts to 500 Heads

[SoloFrenos]

HI, can anyone give me the dimensions of the exhaust collets i will need to fit 350 exhausts into 500 heads, so i can get a set made up please?

Thanks, Tony

[EVguru]

No, I can't.

With a 500 head and a 350 downpipe in front of me, I could work it out, but it's so simple that it's verging on the "Can you look this up on Google for me?" attitude that is so prevelent these days.

A 350 exhaust system won't fit a 500 engine. The downpipes would be too short and the distance between the exhaust ports is greater so the balance pipe wouldn't line up.

[SoloFrenos]

Hmm. not sure why i deserved that kind of response? I Just asked a simple question. If you can't tell me the answer or offer something constructive then i'd rather you not post.

I would work it out myself as i am sure it is simple and verging on the "Can you look this up on Google for me?" but as the bike and heads are 70 miles from where i am currently working, I thought i'd ask the question to see if anyone could help and save me time etc getting them made. But I did not realise i had to explain why i was asking my question.

[vsb]

Measuring some of the scrap in my garage gives these dimensions: 350 pipe has an initial wider section against the exhaust gasket in the head of 33mm stepping down to a narrower section of 28mm, 500 pipe is 38mm dropping to 35mm (all outside diameters). The ID of 350 exhaust nut is 34mm, the id of a 500 nut is 38mm. The od of a pair of 500 collets is 43mm as is the id of a 500 exhaust port thread. Looking at a new pair of 500 collets, the are 11mm wide (or long possibly) the wider 43mm od section is 6mm wide, dropping for 5mm to 38mm to fit inside the nut. The id of the collets is 38mm for the first 2mm dropping to 36mm so they are sort of "Z" cross section.
To fit 350 pipes to 500 heads I guess you need collets which are 11mm wide, with 500 external dimensions ie 43mm diameter for the first 6mm dropping to 38mm for the final 5mm to fit inside the 500 exhaust nuts, but with internal diameters to fit the 350 pipes so 33mm id for the first 2mm dropping to 28mm.
Hope that helps with all the usual declaimers! I didn't have any 350 collets to hand but I did have a couple of old 350 pipes to check.

[SoloFrenos]

Hi VSB,

Thank you very much for that, those are exactly the dims I need to produce the drawing so I can get them made.

Thanks again, tony

[EVguru]

I'm sorry, but you're catching a reaction to last weeks stupid email questions, one of which was...

"Do NLM have website?"


Do you have to explain why you're asking the question? Well, yes, it's often a good idea because the reason may change the answer.

There are enough variations in downpipes and even exhaust nuts that I'd hesitate to make a set from reported dimensions. If you're farming the machining out and possibly even paying for the work to be done, then I'd really want to be sure the parts will fit. Talk to NLM some time about supplying customers with the right type of collets!

[MarkB]

"There are enough variations in downpipes..." Yes, changing the stainless system on my 350 Strada to original steel downpipes, I had to use thinner collets because of the different thickness of the tubing, and the collets on the 350 Sport are different again. NLM stock a number of different size/profile collets, so it may take a bit of experimentation. Rob, who looks after NLM's spares dept, is very helpful.