Possible air leak

jas328sport · Post by **jas328sport** » Thu May 17, 2018 4:33 pm

Starting to think that my rough running low rev problem may be down to an air leak. When the bike is cold it idles cleanly at just over 1k, when hot and you rev it, the revs hang at around 2k for a few seconds, then drop to 1.5k for another few seconds before finally settling at just over 1k but sounding really lumpy and rough.
Are there any common places for air leaks that I could check for.

redapple · Post by **redapple** » Thu May 17, 2018 7:03 pm

I used the washing up liquid/water and spray bottle method and found my carb intake manifold rubbers were cracked and solid as a rock

Teego · Post by **Teego** » Thu May 17, 2018 7:08 pm

redapple wrote:I used the washing up liquid/water and spray bottle method and found my carb intake manifold rubbers were cracked and solid as a rock

That's the best place to start before opening the carbs.

jas328sport · Post by **jas328sport** » Thu May 17, 2018 11:37 pm

That's a good shout as the carbs haven't been off in the 20 odd years that I have owned it. I will certainly give spraying something around the inlet rubbers a go.

jas328sport · Post by **jas328sport** » Sun May 27, 2018 4:17 pm

Well I reckon I may have found the problem with my low rev running problems. I finally decided to bite the bullet today and pull the carbs, I opened up 2 of them and removed the toobs but tbh they didn't look too bad at all, maybe a slight bit of wear but the 2 I removed were still fairly round, the diaphrams were also fine. I then concentrated on the inlet rubbers and I reckon it is pretty obvious why I am having trouble, the are all rock hard and cracked but more importantly there are chucks of rubber missing where the neck of the carb should actually seal, what do you think, this is admittedly the worst one but it does look pretty nasty to me.
https://imageshack.com/a/img922/6128/WR6Lup.jpg
https://imageshack.com/a/img922/686/K9WBz0.jpg

Post by **nuggitt** » Sun May 27, 2018 4:59 pm

I think you can say they are well and truly knackered. Get some new ones on and it should help a lot.

jas328sport · Post by **jas328sport** » Mon May 28, 2018 1:15 pm

How do you disconnect the throttle cables, I can see that the choke is just a matter of undoing the cable clamp but can't see an easy way to do the throttle cables. I was thinking that whilst I am waiting for new rubbers it may be the perfect opportunity to remove the carbs and make sure all the jets and bowls are clean.

Post by **nuggitt** » Mon May 28, 2018 4:20 pm

What I usually do is to undo the round plastic lock nut at the handlebar end so it gives you plenty of slack at the carb end. Then slip the carbs out of their rubbers, then you'll find you can get the nipples out of the large pulley on the carbs quite easily. Sorry I can't give you any photos as my bike is now built up.

It's a bit of a swine getting the buggers back in though. You will have fun and a bit of juicy language too.

jas328sport · Post by **jas328sport** » Mon May 28, 2018 4:37 pm

nuggitt wrote:
It's a bit of a swine getting the buggers back in though. You will have fun and a bit of juicy language too.

That's what I am worried about as when I disconnected the throttle end to reroute the cables it was an absolute pig to get the nipples back in. Ah well if that's the only way then so be it, best make sure my daughter isn't around when I try it

Teego · Post by **Teego** » Mon May 28, 2018 8:40 pm

FWIW here's my take on it.
Tank off.
Get a roasting tin and settle it behind the carbs.
This will catch fuel and any parts that might otherwise do a Kim Jong-Un and disappear into the stratosphere.
Then you can pull the carbs off without undoing any cables.
Rest the carbs in the tin and work on them one by one.
That's what I did and there was a toobs, etc how to somewhere on the site but I can't find it now.
Probably because I don't have carbs anymore, just 16 injectors and a sodding great supercharger. At least I don't have to worry about intake rubbers and toobs anymoe.

Post by **Stig** » Mon May 28, 2018 9:31 pm

This might help. It's not finished so no permanent link

http://www.exup1000.co.uk/tech_info_are ... ntoobs.htm

Teego · Post by **Teego** » Mon May 28, 2018 10:43 pm

This is the link you want:
http://www.exup1000.co.uk/tech_info_are ... gtoobs.htm
Lots of great stuff on this site if you know where to find it.

jas328sport · Post by **jas328sport** » Tue May 29, 2018 12:38 am

Thanks all, I have now ordered a new set of toobs as I figured that I only want to take it all apart once so may as well do it all in one go so that at least I have the piece of mind that it's done properly.

jas328sport · Post by **jas328sport** » Fri Jun 01, 2018 5:01 pm

OK new rubbers fitted and the toobs have arrived today so that's my job for this evening. I have read people talking about how the jubilee clips have to be in the correct position so as not to foul the linkages but does that little notch in the jubilee clips not just slide over the raised lump on the inlet rubber, when I took the old ones off the clips look like they were in completely the wrong position but that had probably been done for ease of access to the screws.

Post by **Stig** » Fri Jun 01, 2018 7:55 pm

You can flip the clips so they still locate in the notches but screws face headstock