Cuts out in the higher RPM's

[tcoop]

I just rebuild the carbs on my 78. Before the rebuild the bike ran pretty good plenty of power in the mid to high RPM's,but was a little hard to start.

Used the kit I got from Georgefix.
The tips to the Air mixture screws were broken off in three of the carbs. I did everything I could to get the old tips out (froze them, used penetrating oil and push pin) and nothing worked so I ended up drilling them out with a 1/16 in bit. I don't know if two much air is getting through now or not. Check the plugs after and they are all a nice light tan.

Replaced all the jets and the float valves (seat and needle). I didn't check the float levels.

Synced the carbs and she now starts and purrs like a kitten with just a touch of the button.

The problem is she can't go over 5000 RPM's. She Cuts out spits and sputters as if she is starving for fuel.

Is this because the float level not being re-set?
What is the best way to set the float level? I don't see a way to check the level like I can with the XJ750.
Is there something else that I need to look for when I pull the carbs back out?

[81xsproject]

If your bike idles okay, which doesn't sound like, it's not the needles. Best way is to use the end of a caliper with the carbs out and upside down on the bench measured from the carb body where the gasket would sit (with it removed) to the top of the round part of the float. Make sure both sides of each float measure the same, dont rub on any part of the body as they pivot, and that those crap brass float don't have leaks. Do you self a HUGE favor. Put the MIKUNI jets (cleaned) back in and get rid of the kit crap. After proper float heights and jets, we'll go from there.

[DAVINCI]

I didn't check the float levels.

She Cuts out spits and sputters as if she is starving for fuel.

Probably not high enough. Float adjustment procedure is in the manual.

[ManagerMike]

I just rebuild the carbs on my 78. Before the rebuild the bike ran pretty good plenty of power in the mid to high RPM's,but was a little hard to start.

Used the kit I got from Georgefix.
The tips to the Air mixture screws were broken off in three of the carbs. I did everything I could to get the old tips out (froze them, used penetrating oil and push pin) and nothing worked so I ended up drilling them out with a 1/16 in bit. I don't know if two much air is getting through now or not. Check the plugs after and they are all a nice light tan.

Replaced all the jets and the float valves (seat and needle). I didn't check the float levels.

Synced the carbs and she now starts and purrs like a kitten with just a touch of the button.

The problem is she can't go over 5000 RPM's. She Cuts out spits and sputters as if she is starving for fuel.

Is this because the float level not being re-set?
What is the best way to set the float level? I don't see a way to check the level like I can with the XJ750.
Is there something else that I need to look for when I pull the carbs back out?

The pilot screws don't affect high throttle angles, but float levels definitely do. The only effective way to set the floats for the 78-79 is to remove the carbs, invert them, remove the bowls and measure the height from the gasket flange to the float as it is resting on the float valve.
Search for any post by member Cataonic Bug, there is a link to free service manual downlaods in his signature. The full details and specs for the procedure are in there. You'll want to re-sync again however.

[psycoreefer]

I had a similar problem after rebuilding the carbs on my 79, but I'm going to wait and see what happens when you check the float level, as it effects all RPM's.
Another clue - do you have to use the choke to start the bike when cold? How about when its hot?

I've found on mine when I had the floats set too rich -> a low number measured from the service manual procedure -> a high fuel level in the bowl, that I didn't have to choke it when cold (or maybe just half choke), after leaning the float levels I find that I have to use choke but everything else is improved.

I also found for me personally it was very hard to distinguish between "flooding" at high RPM, and "Starving" at higher RPM, I'm sure I experienced both in all my carb futzing and I'll tell you they both seem on the bike to be almost identical.

[petejw]

as the others have said how to check
the float heights, to see if they are correct
when riding, have the bike in 4th or 5th gear
with the revs around 2000rpm, crack the throttle
wide open, the engine should accept the throttle
without lag (lean) or bogging down (rich).

[tcoop]

The floats were off by about 1/8 of an inch. The fuel was getting shut off way to soon.

Snow falling right now so I wont be able to test it out until Saturday.

[psycoreefer]

remember that now that fuel level is higher you'll have to go through the idle tunning steps again...

[tcoop]

Thanks everyone

A new member BA80 sent me this link

http://www.iwt.com.au/mikunicarb.htm

that helped me understand the carbs a little more (most of you probably know all the workings of the carbs...I'm getting there. A few more time of taking these carbs apart and I might know something).

[XS1100 Newbie]

I think you have it with the float level, but do be sure to check the idle circuit again, and maybe synch. You did remove the covers for the air/fuel mixture screws? For measurement on my floats, i took an old credit card, and measured and cut very carefully to fit in the right places over both floats at once so i could not only have the right height, but make sure both sides were the same easier.

[windjammergump]

cuts out....

friend here done his carbs ....ran fine till he hit 5000 rpms and after all said and done he had a bad coil....under pressure it was letting him down...replaced his coils and jetted away....

[James England]

get rid of the kit crap.

Could you specify in what way the kits from Georgefix mentioned in the posting are "crap" please?

[crazy steve]

Could you specify in what way the kits from Georgefix mentioned in the posting are "crap" please?

Yeah, I'd be interested in any comments on his kits too. In my recent 'wheelin-dealin' I've acquired several complete sets of carbs, but due to mis-handing by the PO, more than a few of the needle jets are bent and will need to be replaced (among other issues). Georgefix seems to be the easiest/most economical source with what has seemed to be good feedback here.... not true?

[Rasputin]

I have not used carb kits from Georgefix. Possibly the negative response is due to the jets not being geniune Mikuni, if they are not. Everything I have ordered from Georgefix has been correct for my application, fast, prompt, cheap, and not ripped off on shipping. He has been an exemplary supplier of many types of parts for me and will continue to do so.

[cywelchjr]

My understanding was the georgefix kits came with mikuni jets.