80 34mm CV carbs on 78 XS650E w/stock airbox

woodman · Full Member Joined: Oct 12, 2008 Posts: 256

Would this swap be worth doing and will the 34s fit the 78 airbox or will my 80 airbox fit the 78 frame ? XS John are you out there ?

weekendrider

woodman the 34's are longer/deeper. I couldn't fit them to a standards stock air box. 38's on the right 34's on the left. Haven't looked at swapping air boxes.

ady66

Hi Woodman,

I have fitted BS34s to my 80 (ish) roadster but its a very tight fit. I had to discard the original rubbers which join the carb to the airbox and file the airbox outlets by about 1 mm to give enough clearance to get them on. I also have to remove both inlet manifolds each time I remove/refit. I made new smaller rubber seals for the carb/airbox joints out of inner tube and stretched and superglued them in place (don't know how long they will last with the petrol fumes but I'll try to find some thin nitrile rubber for the longer term). They seem to work well enough but it's not yet roadworthy to confirm it's fine throughout the rev range (idles beautifully). The 34s are also wider so I had to bend the front of each sidepanel 'cup' slightly to make enough clearance to get the covers on.

y airbox is stock, but fitted with K&N 'original style' filters, and is the same airbox as my '79 SF. From memory (I fitted them a while ago) the diameter of the 34s was slightly larger where they meet the airbox, which was another reason for needing to remove the original (rock hard) rubbers.

Only reason I fitted the 34s was because my 'project' came in boxes with no carbs, and I had a set of 34s. Eventually I'll probably change them for 38s to make everything fit better (or if I like them better than my 38s on my cafe I'll trim the sidepanels to suit).

So it can be done with a bit of effort, but it wasn't as straightforward as I originally thought.

Good luck with it.

Ady.

woodman · Full Member Joined: Oct 12, 2008 Posts: 256

Thanks for the info, I have an 80 parts bike but I think Ill just leave the stock carbs on the 78 now

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