setting my carbs up

[StuartWags]

I have just swapped out my carbs because of the poor performance and busted mixture screw. I have fitted some that came off a 3000 mile bike but the have been kicking around for years. I gave them a flush through with carb cleaner before bagging and storing them about 3 years ago.

I fitted them and it resolved the issue i had with the old set and they seem much crisper when snapping the throttle from idle (default mixture setting). However, when holding the revs steady at 3000 to 4000 rpm it coughs back into the air box pretty bad. Does the same when ridden and has really bad popping / banging from the exhaust on the over run.

I wound out the mixture screws 1/2 turn each and it seems the same static but not tried riding it yet.

I am in the process of digesting some of the comprehensive carb setting guides but would also like a little help from the pros.

I have not checked the jet sizes on these carbs but at 3000 miles i am assuming they were standard. And cannot rule out crap that may have been lodged in them. These carbs came from a flood damaged job lot and they have had water in them.

[VTRDark]

I'm assuming your vacuum is in the right place on the petcock and not leaking, so the popping and banging will most likely be an intake and/or exhaust leak, so check that over and sort first. As for the coughs, it could be a lean condition. What air filter and exhaust are you running? You may get away with shimming the needles and/or increasing the pilot jet size, but we need to know what it has first.

(:-})

[StuartWags]

I am going to revert as much back to possible and start from there ..... plus buff up on the notes and i will be back

[StuartWags]

what a fanny about.

set 1 - was fitted and were not working well. Front mixture screw crumble when trying to adjust. On stripping the mains were the wrong way round and the front pilot circuit was full of crap (45s).

Set 2 - from a 3000 mile bike. cant go wrong right!!!!!. Rear pilot loop full of crap (48s) and would not clear.

Set 3 - scrap lot on 45 pilots and very grubby, not usable, loads of crap inside. all mixture screws stuck


Out of the 3 sets i now have a Frankenstein set of carbs on 45 pilots ......not road tested yet but i have set everything to default, standard cans etc. and on static test it is pretty good. Although i would still say it is a little lean.

[VTRDark]

One never knows what you might find when you open them up. I once bought an immaculate looking low mileage (so they said) set of carbs. Looked lovely and clean on the outside. Opened them up and.......







(:-})

[StuartWags]

now i have a bass line set i am want to build a set with my jet kit, K&N and carbon cans........... oh joy

[Kev L]

now i have a bass line set i am want to build a set with my jet kit, K&N and carbon cans........... oh joy

Treble your effort and mix it up a bit innit!

[StuartWags]

i have a set of thumb screws on the way, nipple clamps next

[lloydie]

i have a set of thumb screws on the way, nipple clamps next

Try tassels first !! Don't want you going in over your head :-)

[Seven Of Nine Firestorm]

i have a set of thumb screws on the way, nipple clamps next

Try tassels first !! Don't want you going in over your head :-)

^^^^^^^^^^ PMSL

[StuartWags]

Just been clad in new rubber as well.... tyres that is.

[Kev L]

Just been clad in new rubber as well.... tyres that is.

Yeah, tyres, course it's tyres!!!!!

[Bluefox]

Hey Stu did you actually pin point the problem mate,mines doin exactly the
same 3-4k,

[StuartWags]

The simple answer is yes it was a blocked pilot jet.
However, i could not have got there without having a good read through some of the posts here. It is really helps if you can get an understanding of symptoms. i.e. does it get better or worse when it is hot etc. It is a pain in the butt, if you have not got an efficient way of adjusting the mixture screws. I had to remove the carbs to make adjustments, which is ok for the diagnostics but you will not be able to do the fine tuning you need when it is sorted. I took a lot of time, learning, patients and a process of eliminations.



http://www.vtr1000.org/phpBB3/viewtopic ... 14#p238567

http://www.vtr1000.org/phpBB3/viewtopic ... 14#p238528

Summary of what i went through
It took a lot of faffing but i am got it running about right in standard trim (took the cans, reset the TPS).

The bike was running ruff and i suspected it was lean on the front pot as it seem to get much hotter than other vtrs, particularly on the down pipe. It run lumpy all over and did not pull cleanly. Took the off and bust a mixture screw. When i did strip them they were a mess. The main jets were the wrong way round, the pilots were 45s and the remaining mixture screw was set for 48s.


So i swapped them out for a spare set and that's when the coughing in the air filter started. When i checked the mixture screws they were well lean. I put them in the default position and there was an improvement. Wound them out some more and more but the lean symptoms did not get any better. i.e. still coughing at 3 - 4k static test. All all sorts of farting and cracking out the cans on the deceleration / over run.

I stripped the carbs and the rear pilot was so i cleaned the best i could. It seemed a lot better for a bit and then went bad again. At least i knew i was now looking in the right area. i was pretty sure that the pilot drillings were also full of crap as on stripping again the pilot was blocked again

I also found that by removing one of the plug caps, that i could get it do idle on the front pot but not on the back.

I bit the bullet and took the good bits from the carbs i had, put the standard mains and pilots in, set the mixture screws to default and refitted.

Bingo. There or there abouts, just an occasional cough when the throttle is shut on a deceleration. I just need to do the fine tuning now.

[VTRDark]

Well done mate sounds like your winning. Good to hear some of the write up have been of use.

(:-})