Cuts out in the higher RPM's

[Rasputin]

They may very well come with Mikuni jets! As I said I have not used Georgefix's carb parts.

[James England]

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?

I rebuilt my carbs using Georgefix kits. Firstly, the original jets were so badly gunged up and actually corroded that cleaning them would have been pointless. Secondly, none of the "crap" brass floats in my carbs had anything wrong with them whatsoever. Thirdly, after responding courteously and quickly to my questions, Georgefix supplied me with 4 kits which arrived in the UK within 7 days. They contained everything needed to replace the unsatisfactory parts of my carbs yet cost substantially less than other kits which are only a float bowl gasket and float needle valve assembly. I put the carbs back on the bike and it started immediately. I've ridden it a lot since then... it feels like a completely different bike... responsive and smooth. The bike ticks over like a drum machine, the beats are so even. It runs perfectly and is hugely better than before the kits. That's why I'm bemused somewhat by the comment that the kits are "crap", with no explanation or elaboration as to why the person saying this thinks that. Same goes for the floats.... mine are 31 years old and still absolutely fine. Same with the floats on another set of carbs which I recently acquired.

Based on my own recent experience of using a carb rebuild 'specialist' (thread posted already about this), I'd definitely recommend doing one's own carb rebuild using George's kits. At least the bike will run afterwards

[tcoop]

I don't think the jets from Georgefix are genuine Mikumi. That being said they don't look any different than the ones that were in the carbs (except for the size stamp, same size just stamped differently).

Just for kiks I pulled the carbs pulled all the jets cleaned all the holes and put the old Jets back in,(never messed with the needle attached to the diaphram slide)

pulled the fLoats, needle and seat made sre the screens were clean and reinstalled them
re-set the float hight to the specs in the manual.
Made sure the Diaphrams were good and properly placed
re-synced the carbs and took it for a test ride.

At Full throttle It pulled strong from 1000 rpms to 4000 rpm, stumbled from 4000 to 6000 then took off like a raped ape (as they say) from 6000 to redline.

At half throttle it pulled smoothly through out the band

Before doing any changes it ran with no problems other than the floats not shutting off the fuel.

[James England]

If, on putting the carbs back onto the bike, it runs fine, I really don't mind at all if the jets aren't genuine Mikuni. The diaphragms I used certainly aren't. Many 'pattern' spares are made by the same manufacturer that supplies people like Yamaha, Mikuni and so on. eg. the inlet manifolds currently available on eBay. I bought some. They are not branded Yamaha but they are made by the same manufacturer who supplies Yamaha and are identical in every respect. Brembo brake pads are not Yamaha, many after-market oil filters are not genuine Yamaha, many oil seals are copies. Most bearings are not OEM. People replace entire air filter systems with non-Yamaha parts. Geezer's new valves aren't OEM and nor is his regulator rectifier which I put on my bike.

Personally, I think if a spare does what it's supposed to do, for a reasonable length of time, and is of good enough quality, then it doesn't matter who makes it, especially if the bike it's intended for is at least 20 years and half the parts aren't supplied by the OEM anyway.

I just took my bike out. Smooth, powerful, pulls smoothly up through all the range, no pops, bangs, explosions. No fuel starvation, no flooding...just a nice ride. It's all ruined for me though as I suspect the jets and diaphragms may not be genuine Mikuni

[psycoreefer]

I've had no problems with georgefix's stuff from e-bay. In fact he went out of his way to replace a set of petcock kits that disolved for some unknown reason while I was at the cali-rally last year, he didn't have to but he did, for free, and I've had no issues with the new ones.

That said I would prefer genuine parts if they were available for a reasonable price.

Tcoop - I've been fighting a similar stumble for a long time on my bike, I've had some improvment by raising the needles a single notch -> moving the clip down one notch - to richen the "mid range", although I think my fuel economy suffers a bit for it. I've not spent a lot of time on it after doing that as the stumble is very much improved and I got really sick of working on carbs...

[tcoop]

I'm going to check fo any carb leaks, if that does not fix the issue I will do as you have done with the needle.

I don't think the issue is with the kit I got from Georgefix. I think the carbs were "tuned" to a out of tune engine (PO). And now I want to get everything running right.

[81xsproject]

Before doing any changes it ran with no problems other than the floats not shutting off the fuel.

Another good reason to go back to square one with stock jets. Jets aren't a wearing parts, they just get dirty. It's always worth checking on the slide needles if you haven't ever. I find all the time where PO's have adjusted the needle clip in 70's carbs.

[tcoop]

I put the old jets back in. It runs a little better but still get the stumble around 4000 to 6500 rpms. It feels like two cylinders are not firing during that range. I was thinking it was a vacuum leak (the vacuumed caps were hard and cracked replaced them but still no go).

I'll do a plug chop as soon as I can to determine which cylinder's are the problem.

[DiverRay]

Once you find out what pistons are not working, you can probably fix it easily. My guess will be the float height may need to be adjusted a little "closer". When you adjust the float level, ALL EIGHT FLOATS NEED TO BE THE SAME HEIGHT! If you have just one off a little bit, it can change the fuel level in the bowel. that can change the rate of flow through the jet, and give you a stumble problem like you have.
The other thing that can cause a problem like that is a wire that is ALMOST gone on the pickup coils. I would think a much lower chance, but still a chance.

[cywelchjr]

Once you find out what pistons are not working, you can probably fix it easily. My guess will be the float height may need to be adjusted a little "closer". When you adjust the float level, ALL EIGHT FLOATS NEED TO BE THE SAME HEIGHT! If you have just one off a little bit, it can change the fuel level in the bowel. that can change the rate of flow through the jet, and give you a stumble problem like you have.
The other thing that can cause a problem like that is a wire that is ALMOST gone on the pickup coils. I would think a much lower chance, but still a chance.

8 floats? Don't you mean 4 floats and they must be level?

I mean, I understand your meaning, but someone less experienced might not understand.

[crazy steve]

What he means is there's four sets of two floats (tied with a cross-piece) and you need to check each one individually. I know that's important, because when I checked mine I found 3 of the 4 were tweaked and needed adjusting to get both floats at the same height. Otherwise you'll just get an 'average' of the two and maybe even a bit of binding...

[81xsproject]

...Make sure both sides of each float measure the same, and dont rub on any part of the body as they pivot, and that those crap brass float don't have leaks...

This all sounds so familiar