Sudco Carb replacement kit

[flyingdakota]

So I went to Sudco's website ( http://www.sudco.com/Catalog37Digital/index.html#/128/ ) and found that they make a replacements racing carbs for the XS11, comes with everything to attach them, he says it gives it a snappier throttle and better top end. But the bad news is, they are $942.90 +shipping. Has anyone ever installed these carbs on their machine, and if so was it worth it? My bike runs really good except it stumbles around 6K if you pin the throttle, if you ease into it, it does better but still stumbles.
Cheers!
Tim

[D0wn5h1ft]

Go to the product reviews section on this forum and you'll see a post about the CR33's. if you're looking for a good (albeit expensive) replacement those are your best bet and they are cheaper at ~$850. If I had the cash I'd do those or the RS34's by mikuni just because I'm at least familiar with where to find mikuni genuine parts already.

[flyingdakota]

The sales guy told me the CR33s were basically what I had for performance wise...but I figure for an extra $100 to get the CR34s with a better top end I would go that way. I have a 4 into 1 Kerker exhaust and it has be up sized in the jets but it just seems like it could run better. I think it might still be lean...with that said I have NO idea what jet is in there now....It has been10-15 years since I had the carbs apart and I didn't write anything down in the book. I messed with them for like 2 weeks trying to get it to run the best I could....Maybe I should revisit them again....problem is, that is finally riding weather and I don't want to pull it apart! :P Maybe a winter project. If I had the money I'd probably do it since it sounds like a bolt-and-ride type application...Is there really such a thing??!!:P
Cheers!
Tim

[flyingdakota]

Ok, read the review speedmoto wrote...sounds like the 33's would be adequate, especially if he was running basically a straight exhaust....hmmmm.....hmmmm....Must get back to work and make some $$$
Cheers!
Tim

[D0wn5h1ft]

The sales guy told me the CR33s were basically what I had for performance wise...but I figure for an extra $100 to get the CR34s with a better top end I would go that way. I have a 4 into 1 Kerker exhaust and it has be up sized in the jets but it just seems like it could run better. I think it might still be lean...with that said I have NO idea what jet is in there now....It has been10-15 years since I had the carbs apart and I didn't write anything down in the book. I messed with them for like 2 weeks trying to get it to run the best I could....Maybe I should revisit them again....problem is, that is finally riding weather and I don't want to pull it apart! :P Maybe a winter project. If I had the money I'd probably do it since it sounds like a bolt-and-ride type application...Is there really such a thing??!!:P
Cheers!
Tim

You should try and diagnose your symptoms with the help here on the site before you drop a grand into new carbs. There is VERY little difference between the CR33 and the CR34 just that in the 34 you lose low end because the venturi is too large. With a 4 to 1 Kerker your bike should run even better than mine since I run straight pipes. Stock carbs can be made to run excellent with a 4 to 1 and I know this because my '78 had a 4 to 1 and it SCREAMED. Those racing carbs are really meant for one purpose, racing. They lack the constant velocity feature that the stock carbs have which means you have to be way more disciplined with the throttle or you'll stall out the bike.

Your problem is mostly likely jetting. If you haven't already, I'd start by going all the way back to stock jetting and work from there. There's no reason that a kerker exhaust with stock carbs shouldn't work for you because countless others have done it on this site with lots of success. A throughout cleaning and MINOR jetting adjustments (if any) will leave you happy. The 4 to 1 exhaust have a much higher exhaust velocity compared to other setups which means they'll suffer a bit on the top (5750 RPMs and up) end but low and mid will stomp even the stock exhaust

[natemoen]

You have to remember that these racing carbs are meant for legend cars. Many of them ran XS11 engines back in the day (and many still do).

[flyingdakota]

OK, Yeah it runs great on the bottom end, and right about 5500rpm to 6K is where it starts to stumble...if I pin it. If I ease into it it'll be better but not perfect. I think I'll have to pull the carbs again and check and see what size jets I have. ugh...
Cheers!
Tim

[natemoen]

OK, Yeah it runs great on the bottom end, and right about 5500rpm to 6K is where it starts to stumble...if I pin it. If I ease into it it'll be better but not perfect. I think I'll have to pull the carbs again and check and see what size jets I have. ugh...
Cheers!
Tim

Also check and see what notch your needle is set at. Put it in the center notch if it is not in that position.

[motoman]

The sales guy told me the CR33s were basically what I had for performance wise...but I figure for an extra $100 to get the CR34s with a better top end I would go that way. I have a 4 into 1 Kerker exhaust and it has be up sized in the jets but it just seems like it could run better. I think it might still be lean...with that said I have NO idea what jet is in there now....It has been10-15 years since I had the carbs apart and I didn't write anything down in the book. I messed with them for like 2 weeks trying to get it to run the best I could....Maybe I should revisit them again....problem is, that is finally riding weather and I don't want to pull it apart! :P Maybe a winter project. If I had the money I'd probably do it since it sounds like a bolt-and-ride type application...Is there really such a thing??!!:P
Cheers!
Tim

No bolt-on fix for carbs with electrical issues......as in prim/sec. ignition issues, which is what your bike has.

[D0wn5h1ft]

OK, Yeah it runs great on the bottom end, and right about 5500rpm to 6K is where it starts to stumble...if I pin it. If I ease into it it'll be better but not perfect. I think I'll have to pull the carbs again and check and see what size jets I have. ugh...
Cheers!
Tim

You're too rich on your mains. I had this same issue. Stumbling means too rich as long as it's not a fuel starvation problem. If you have aftermarket (Dynatech) coils and a strong spark you can open up the gap on your plugs a bit more to help with this too. Stumbling due to a lean condition is pretty severe. Usually, a lean condition on the top end results in a loss of power (such as a dip on RPMs at a certain throttle opening). A lean stumble is pretty hard to do because it would suck all throughout the power band and not just hit a wall like you're describing.

A quick trick I used to figure out my rich condition was to advance the initial ignition advance by about 10 degrees. The stumbling will get better but this isn't a fix because it will never go away if you're that rich.

I left my initial advance at 10 degrees just because I can run a little more rich without any super-adverse side affects but then again I'm running straight pipes...

[flyingdakota]

Ok, I'll try that...So advance 10 degrees and if it still stumbles it's rich and if it is better and doesn't stumble it'll be a lean condition?
The coils I have are aftermarket but again I have NO idea what brand they are. I had an ignition problem when I first bought it and replace the wiring on the pick ups, then found the coils were out of spec and found a set of new replacements that you could fab your own wires. (installed new wires, plugs and caps too) And that too was 15 years ago.
I'll check the needle setting too, I remember that was one of the things I tried and I ended up putting back to the original notch.
Cheers!
Tim

[D0wn5h1ft]

Ok, I'll try that...So advance 10 degrees and if it still stumbles it's rich and if it is better and doesn't stumble it'll be a lean condition?
The coils I have are aftermarket but again I have NO idea what brand they are. I had an ignition problem when I first bought it and replace the wiring on the pick ups, then found the coils were out of spec and found a set of new replacements that you could fab your own wires. (installed new wires, plugs and caps too) And that too was 15 years ago.
I'll check the needle setting too, I remember that was one of the things I tried and I ended up putting back to the original notch.
Cheers!
Tim

If it stumbles less when you advance the ignition it means you are too rich on the mains.

[flyingdakota]

ok I understand that, but what about a lean condition (too small of a main jet)? Would it clear up or get worse?
Cheers!
Tim

[D0wn5h1ft]

ok I understand that, but what about a lean condition (too small of a main jet)? Would it clear up or get worse?
Cheers!
Tim

You won't notice a difference. In the absolute worst case your engine will start pinging (detonation) and then you've got your answer. Usually though it take a lot of advance to get it to start pinging even if it's running lean.

A way to check if it's lean on the top end too is to open your choke to full. If it starts pulling hard again, consistently, when you do this then it's definitely a lean condition. HOWEVER, this doesn't specifically mean that it's because your mains are too small. It could also mean a fuel starvation issue caused by floats set too low, clogged fuel lines, petcocks clogged or vacuum mech not working, bad gas tank ventilation, dirty carbs, the list goes on.

[Bonz]

Pick up a set of ZRX carbs off ebay. A lot cheaper and from everything I have read, will wake the bike up and not lose fuel efficiency or driveability.