Anybody out this afternoon?

Going to Rye about 1300-1330ish. Anybody ?

 

Well I went out today to test my old carbs, back on the bike as I had to return the borrowed carbs to the owner. Sure enough they keep bogging down coming out of corners Anyway had a blat around the Marsh , returned to Rye and spotted a beautiful MV Agusta heading toward the Canal road. Followed him , passed him , he passed me etc. etc. Stopped for a brew and a chat and carried on to Brenzett, Ivychurch, New Romney, Lydd, Camber. Back to Rye for a coffee in glorious warm sunshine, then did the Wittersham road to Tenterden and arranged to meet again. Couldn't persuade him, Jim , to join our Forum , but he may join us for a rideout one day.

 

Do you know why they are misbehaving, Alan? Sticky floats? If they don't bog while accelerating in a straight line, that rules out whatever is the modern equivalent of advance/retard; perhaps the floats are rubbing against the sides of the barrels. Is it more on lefts than rights? More at low engine speeds than at 9,000 rpm?

 

It's at between 4500 to 6500 revs mate. Have checked everything and 3 different sets of carbs. I borrowed a mates and the problem went away. How can 3 sets of carbs give the same problem ???

 

Did you check the needle sizes of all the sets? I'm just wondering if that one magic set had been rejetted. After all, if you have a new exhaust (and maybe a free-flow filter?) the bike will need more juice and a bigger main jet. If the starvation symptom comes between 4,500 and 6,500 rpm, that's when the main jet is starting to open in earnest. And if its profile ain't big enough... you get the picture.

 

Flat spots in the rev range usually points to incorrect jet / needle. Given you're running a custom exhaust (and aftermarket filter?) a change of jet would seem in order.

**edit** Rich added the same thing I said as I was writing it! Wasn't plagurising, honest

 

Careful... you're starting to sound like you know what you're talking about and we wouldn't want that now would we?

 

Oh dear. I know about cars. Not bikes. You are right, Hanna: I should have warned MegaPerson. Oops... I'm banking on bikes being smaller versions thereof and working on basically the same principles. Still if Skortchio said it too, I must be on the right lines, no? 'Course, the pudding will prove in the unscrewing

...of the needles to see what size they are.

 

All 4 sets of carbs have been dynojetted with different mains, needle settings and pilot jet settings, but I will be copying the other carbs again to check. Otherwise it,s dyno time.

 

Probably the fastest / best solution all round, assuming you're finalised with your exhaust alterations. Course does mean actual monitary outlay, but max potential is worth the pennies I'd say

 

Thanks Dave, but I don't understand how one set of carbs worked perfectly on the trackbike with the same exhaust and won't work on my bike. I will probs end up paying between 100 and 300 quid to get em sorted, but it's the fact that I can't find what's wrong with 3 sets of carbs that really pi$$es me off!

 

Know what you mean, fella. I had a similar problem with my TL years ago, swapping known working parts only worked 1 out of 3 times for no apparent reason. Different engines all have different characteristics of course, such a drastic drop at only one point in the rev range points to fueling. If it was any time you opened the throttle hard then could be float chambers or vacum issues.
Hope you get it sorted one way or another, DHR should be able to set you up pretty fast as there's only one flat spot and you can identify it should save time too. Wouldn't expect it'll be more than £100. But I could be wrong

 

Thanks for advice and encouragement Dave. I will be changing engines and exhaust systems this summer, so I will just tolerate the flat spot till then.

 

Even better! Just stay well above 6.5k rpm, problem solved

 

Now that you mention it, I Didn,t have much trouble on a trackday at RAF Odiham last year. Perhaps a quickshifter would help as well?

 

Hehe, they always help!