TOPIC:

Hi, I have my carbs set so the bike finally runs. I've been on two six hour trips and the bike moves resonably well.

My question - ongoing pain - is what's up with my carbs.

I have pods and a baffled 4-1 exhaust. The bike runs fine 4500RPM and up. from 2-4500RM it's reluctant to accelerate. under 2K RPM and I have to apply throttle to keep it going. To top it all off, this i only with the choke totally ON!!

As soon as a turn the choke ofm the bike dies - en with throttle. The carbs are clean, every hole, jet etc!! I made very sure.

I have screws on the carb tops on the motor side. When closed, the bike has NO POWER. When opened to the maximum, the bike has reasonble power, but still needs the choke to function.

Please, any advice would be appreciated.

What size jets do you have?

i had that problem with my 700, i thought i had cleaned the carbs very good but found out that there were tubes that the main jets screw into that were plugged solid with rust had to pull them out and clean every little hole on them (there are many) these tubes supply fuel to the pilot jets, I'm assuming you have bs34 mikuni's?
if so make sure you put the caps back on the pilot jets other wise you wont have fuel to the idle circuit

hope this helps

If your carbs are Keihins then the pic below may help. I have pods and 4->1 and bike runs well with this setup. The mixture screws on the top on the carb engine side should be 2 turns out.

If your carbs are Mikunis then hopefully someone else can help.

Unfortunatly, the Keihin CV34s don't have any replacement pilot jets that are larger than the stock #35s available. The Keihins use both a secondary main jet and a main jet where the secondary main jet is the one pictured as a #135 in JRs excellent picture. This jet controls wide open throttle (mainly). The smaller main jet pictured as a #62 operates mainly in the mid-range in conjuction with the position of the jet needle. I suspect someone will figure out the correct drill bit at some point to get the #35 pilots up to about a #40 where they need to be with pods. This would help the idle and off idle transition quite a bit. JR has chosen a MUCH larger than stock 2nd main jet as the stock size for an 82 Spectre 750 is a #95 and his main jet is a #62 which is smaller than the stock size for the Spectre (#65)... I think that if I were rejetting, I would go with a larger pilot via drilling if possible, a #68 main jet and about a #130 secondary main jet. The larger MAIN jet would help in part to compensate for the too small stock pilot jet... Your mixture screws are all the way out as the bike is very lean at the bottem end of the rpm range in the pilot circuit... the secondary main starts to have effect after you just transition out of the pilot circuit to mid-range.

Post edited by: wiredgeorge, at: 2006/07/11 08:47

Thanks for the help everyone. I think I'll just drill out the jets (at a machine shop). Does anyone know the drill bit size I would need?

Thanks. Might abyone have jets could buy?

Drilling jets must be done with the jet gripped in a vise or clamp and a drill press used. The reason is that you will oval the hole otherwise. In addition, some jets require a bevel for gas to be atomized adequately and not come out in a blob... there have been mucho problems with aftermarket jets (especially pilot jets) that didn't have the OEM style bevel on the edge of the hole so drilling may or may not work well. For Keihin pilots it is about the only answer since you can't buy them but I would hesitate because if you mess them up... well, you can't buy them. You can get Keihin secondary and main jets and I would NEVER drill these as drill just is a poor idea due to the very good chance of messing up functionality of the jets.

I just want to add a quick question. This bike's fuel system is stock (pretty much) other than pods and a 4-1 exhaust. Has anyone ever heard of this problem before? I mean, would such changes warrwnt NEEDING the choke 100% of the time?

If you are needing to be choked to run, that means that the air/fuel mix is otherwise way too lean which pretty much means that there is an air leak somewhere.

Check the SMALLLLLLLL orings under the washers under the springs under your mixture screws. Check the intake manifolds for leaks by spraying with WD40 as the bike runs. This will kill the bike or it will white-smoke if there are leaks. Check the carb connections. Check the vacuum lines and vacuum caps for leaks. In other words, look for air leaking into the carburetors as the bike runs making the air/fuel mix extremely lean!

I'll try exactly that tomorrow morning .... gas is to expensive to choke away!!

Hmmm ... I have a gasket kit too

Lemme know what you think!

I totally redid the carbs today. I took every piece apart and soaked every brass jet/fittign in cleaner.

I found some dirt in some of the jets/holes and actually repaired a tear in the diaphraghm. Upon putting it all back together the bike runs way more powerfully.

With the choke off, it runspoorly with applied throttle. With the choke on, it's a monster

I can thin of only two reason why I'm still having trouble. Firstly, the flat washers and oring on the mixturescrews need replacing. Secondly, there are two open hard plastic ports in between carb 1/2 and 3/4 and I have no idea what to do with them. I have K carbs.

How do you like the dark look? Any suggestions?