No problemo

Sounds like the pilot screws are off... i'd start by balancing the carbs and turn the pilot screws out half a turn.

That'll richen out your idling mixture.

They do usually conk out if you give them some throttle until after about 10 / 15 secs of choke.

2.5 turns is about right.. thats 900 degrees (helps to put a marker on the screwsdriver so you know when you've gone a full turn) as a lot of people only do half a turn!

Let me know how your gettin on.

I will double check the idle screws and im hoping my mate is going to balance the carbs at the weekend.

At the moment at cold it seems to be choking itself as if to rich because it strugles right at the very intial pickup o throttle. this is with choke on or off?

i will keep you posted.

cheers dave

Too rich / Too lean has simliar symptoms at idle. I'm assuming you don't have any air-leaks..

Have a read of this Carb Tuning Guide

It's one of the best explained write ups I have in my favourites. Be sure to read it from the top and not just goto the idle / low rpm section :)

If your still stuck after you've had them balanced / checked let me know.

Neosophist wrote:Too rich / Too lean has simliar symptoms at idle. I'm assuming you don't have any air-leaks..

Have a read of this Carb Tuning Guide

It's one of the best explained write ups I have in my favourites. Be sure to read it from the top and not just goto the idle / low rpm section :)

If your still stuck after you've had them balanced / checked let me know.

Cheers for the link, ive had a read and my bike does sound like the lean mixture screw syndrome.it does hold revs for a few seconds then drop off. But then idle varys some times when i pull up it will be at 2k then anouther it will be less etc. Its very confusing . It just dont wanna tick over when cold at the moment needs constant blipping.

I didnt get a chance to check mixture today, didnt fancy it in the rain.

One thing i did look at when i stripped carbs is how much the throttle butterflys were open, i wedged the throttle arm on the carb open with a screwdriver so it was in a fixed position then used a 1mm drill blank to check the gap between the carb body and butterfly. The blank went under the front but not the rear butterflys. This would point to being out of balance would it not? i know its a rough guide but i assumed they should all be the same?

I didnt alter them as feared i would make it worse without a set of gauges!!

Im pretty sure i dont have any air leaks the carbs are on new inlet rubbers and i couldnt push them down any further or do clamps up any tighter. The vac tube is new too so think that covers everything??

Thanks for all your help, i will keep you posted.

cheers dave

right had a look at the pilot screws, they were 2turns out so tried it at 2.5turns out and no change, tried 2 1/4 and also 1 3/4 but no luck on the cold tick over issue.i have put it back to 2turns for now as it smelt rich from exhaust at 2.5turns.

i checked for airleaks aswell, sprayed wd-40 type spray all over inlet rubbers etc when bike was ticking over at 2.5k and also at 1k but no increase in revs so no leaks?

all i can hope is carb balancing cures it

are my settings right?

pilot 35
main 115
float height 6.8mm
pilot screw 2turns out

settings same on all carbs.

cheers dave

Yeah that sounds about right.

Bear in mind that those are all factory defaults and you may get better results with some fine tuning... balance the carbs first anyway and see how you get on. (I find the morgan carbtune and their right angle screwdriver great for doing this job)

If your still not happy my advice would be to try and find somebody local who's familiar with V4 tuning and get them to sort it. I spent a day at a dyno's not too far away and the mechanic was very familiar with VFR400's, knew where all the flat spots were likely to be, how to cure them etc. Was money well spent.

Neosophist wrote:Yeah that sounds about right.

Bear in mind that those are all factory defaults and you may get better results with some fine tuning... balance the carbs first anyway and see how you get on. (I find the morgan carbtune and their right angle screwdriver great for doing this job)

If your still not happy my advice would be to try and find somebody local who's familiar with V4 tuning and get them to sort it. I spent a day at a dyno's not too far away and the mechanic was very familiar with VFR400's, knew where all the flat spots were likely to be, how to cure them etc. Was money well spent.

Thanks for being so helpful

i just bought a set of cartunes, really easy to use, did it in a hour and it was my 1st try. it ticks over alot better when warm and is smoother, the front and rear carbs were quite a way out but match in there pairs.

im going to keep tinkering with the mixture start from cold is still not good, wont take choke but thinks about it now then starts to splutter and die.will tick over at real low revs from cold without choke though then dies if you put it on.

wanna try and cure as much as possible without the need for a garage, had bad experience in the past.

cheers dave

Aah.. well in the worst case, maybe somone on here local to you could recommend a good mechanic?

If its running without choke it's not right. They usually always need choke for at least 20 - 30 secs from cold.

Have you checked your choke levers are retracting as far into the carbs as possible and their not 'stuck' partially open?, when you were messing with the carbs did you take the tops off and clean under the diaphrams and check them for splits? the carb mechanism works under here and when you pull the rods in / out you'll see.

It is hard to try and diagnose something over the net though as without seeing it I might be missing somethign blindingly obvious.

Do you have the carb microfiche, just to make sure there all put together properly?

Neosophist wrote:Aah.. well in the worst case, maybe somone on here local to you could recommend a good mechanic?

If its running without choke it's not right. They usually always need choke for at least 20 - 30 secs from cold.

Have you checked your choke levers are retracting as far into the carbs as possible and their not 'stuck' partially open?, when you were messing with the carbs did you take the tops off and clean under the diaphrams and check them for splits? the carb mechanism works under here and when you pull the rods in / out you'll see.

It is hard to try and diagnose something over the net though as without seeing it I might be missing somethign blindingly obvious.

Do you have the carb microfiche, just to make sure there all put together properly?

A recommendation would be good, if not a local meber who could take a peek??

Yeah i cleaned under all the diaphrams, i didnt take the chokes out, didnt want to upset the linkage, im prety sure they are all working correctly, i checked them before i stripped the carbs but i will check them again.

If you start it with choke the revs slowly climb for bout 3 secs to 2k then drop off and die, apart from this its runnig the best it ever has!!

i did have a print out of the thing somewhere but cant find it. do you have a link for me??

thanks again dave

Ive had an idea, probably wrong but wanted to run it past you.

when it starts from cold i always get the impression that its too rich, i get a wiff of petrol sometimes and also get the smell sometimes in traffic. the pilot screws are set on the lean side so i was wondering cold i have a dodgy float valve? if its leaking would petrol leak into the bores over night?

or mabye worn pilot screws. they looked good though when had them out but the float valve seats were full of scale like material that i cleaned out but now im wondering if they are seated properly?


cheers dave