5-6k srumble

[rangerguy302]

Ok, I've got a problem with the jetting I believe. How do you Ballance the jetting so it doesn't stumble between the Jets? From idol to 3200rmp smoothe as silk, 3200-about 3800rpm stumbles, 3800-about 5200 smoth as silk, 5200rmp- about5800 stumbles, 5800+rpm rocket ship. Any advice is good advice, thanks for reading

[TopCatGr58]

Hey Ranger,

Well, you're not a newbie, 50 posts since 2014, but you didn't give us much info about your bike, what you've done to it, any mods, etc!?

That description of on and off stumbling sounds more like your carbs are having electrical problems!

Pick Up Coil Repairs: http://www.xs11.com/forum/showthread.php?t=543

Does your bike have any mods, intake, exhaust, etc.? Have you ever fully disassembled the carbs and cleaned them, then vac. synchronized them?

Running OEM ignition parts, coils.

T.C.

[motoman]

Hey Ranger,

Well, you're not a newbie, 50 posts since 2014, but you didn't give us much info about your bike, what you've done to it, any mods, etc!?

That description of on and off stumbling sounds more like your carbs are having electrical problems!

Pick Up Coil Repairs: http://www.xs11.com/forum/showthread.php?t=543

Does your bike have any mods, intake, exhaust, etc.? Have you ever fully disassembled the carbs and cleaned them, then vac. synchronized them?

Running OEM ignition parts, coils.

T.C.

+1 on carbs being the issue, and on ALL of the above. Float settings first. Secondly, idle mixture settings are way off. Thirdly, sync of all four carbs is way off. CORRECTLY check and take care of those issues FIRST, in that order, then report back...that along with more info of bike, and mods if any,etc. Guessing or 'that's close enough' on any of those three doesn't 'cut it', period. BTW, stock jetting(mains/pilot jets) NEED to be stock if no mods(exhaust/air intake) have been done. Since being vacuum operated slides, no jetting is NEVER needed, no even in your location(your elevation bout same as mine here in Grand Junction). From my original location(Durango, Colo., 6,500ft. elev.) where I bought mine new, it run perfectly all the time up to and way over 10,000ft. elev. with stock, original jetting.

[motoman]

+1 on carbs being the issue, and on ALL of the above. Float settings first. Secondly, idle mixture settings are way off. Thirdly, sync of all four carbs is way off. CORRECTLY check and take care of those issues FIRST, in that order, then report back...that along with more info of bike, and mods if any,etc. Guessing or 'that's close enough' on any of those three doesn't 'cut it', period. BTW, stock jetting(mains/pilot jets) NEED to be stock if no mods(exhaust/air intake) have been done. Since being vacuum operated slides, no jetting is NEVER needed, no even in your location(your elevation bout same as mine here in Grand Junction). From my original location(Durango, Colo., 6,500ft. elev.) where I bought mine new, it run perfectly all the time up to and way over 10,000ft. elev. with stock, original jetting.

....as they ALL should, will, and do.

[BA80]

The 78 79 engines have a slight stumble right there on WOT. It's the cams.

About 3300 is where the power really kicks in. My E and both 79 engines had it.

[skids]

Ok, I've got a problem with the jetting I believe. How do you Ballance the jetting so it doesn't stumble between the Jets? From idol to 3200rmp smoothe as silk, 3200-about 3800rpm stumbles, 3800-about 5200 smoth as silk, 5200rmp- about5800 stumbles, 5800+rpm rocket ship. Any advice is good advice, thanks for reading

Here is my take: Vacuum synch and pilot screw adjustment are primarily for the idle circuit which is idle (of course) and up to about 3000 rpms. At 3000 rpms and above, the midrange begins to take over. Midrange has a lot to do with the main needles lifting and the taper on the main needle allowing more fuel into the main jets. The faster rpms (throttle position) will eventually lift the main needle to where the main jet oriface has the most influence. I say, if you have good idle, and smooth even pull to 3200 rpms, your synch is not "way off". Also, if wouldn't tinker with the pilot screws or pilot jets if that is the case. So, why the stumbling at certain rpms? Like Bonz said, it could be fouling pickup wires, but this might also be apparent when you goose it at other rpms, which makes the pickup wires move (I think). Also, stumbling at certain rpms can indicate exhaust system issues...

[BA80]

Also, stumbling at certain rpms can indicate exhaust system issues...

I agree wholly with this line. Speaking from experience.

[Bonz]

To the OP, let us know your set up like TC queried. Did the bike just start doing this or have you finally decided to do something about it because it's been doing it for a good while?

Skids, thanks for the props on the pick up coil, however I haven't posted in this thread yet. LOL. I have CRS as well... TC got confuzzled when I posted information from one thread into another because I was being a post-aholic over the weekend.

I would put a good dose of Seafoam, Berrymans or Techron through a tank of fuel and see if that does anything. Sometimes that stuff actually works.

Otherwise I think skids is right on the money. The pilot jet and pilot screws are probably OK and the sync is probably pretty close too. If running cleaner through a tank of gas doesn't do anything, pull the carbs and clean the main jets. Or give the carbs a thorough cleaning. Count the number of turns the pilots screws are out from lightly seated so you can set them back the same when you're done. Doing a full clean will let you clean the pilot circuit as well it's not going to hurt anything.

[BA80]

You can clean, rejet, and adjust those carbs till the cows come home but that transitional stumble in the cams won't go away. You think I didn't try everything possible on 3 separate engines and 3 separate sets of carbs to eliminate it?

The only time it was really minimal was when I was running the Mac 4 into 2 headers wide open. These early engines LOVE a free flowing exhaust. It does however take a little away from the bottom RPMs.

[Bonz]

I can absolutely agree with your experience, however the OP hasn't been back to answer some questions. If it just started, we both know it's not the cams.

When you talk transitional stumble, you indicate it is around 3,300 rpm. He says it isn't a one time stumble, but from 3200-3800 it stumbles. Does the transitional stumble go away then come back like the OP says at 5200-5800?

I definitely understand the stumble from cams, and the headache of trying to tune it out. I dealt with it from 2800-3300 rpm when I installed ZZR 1200 cams in the ZRX. I changed to a different header system and got it fixed. I tuned and adjusted the carbs until the carbs were tuning me.

Anyway, the OP has plenty of stuff to get back to us about.

[skids]

Skids, thanks for the props on the pick up coil, however I haven't posted in this thread yet. LOL. I have CRS as well... TC got confuzzled when I posted information from one thread into another because I was being a post-aholic over the weekend.

Haha! I got you confused with TopCatGr58.

[Bonz]

I'll take that any day! He's the one that might not want to be confused with me though.

[TopCatGr58]

I'll take that any day! He's the one that might not want to be confused with me though.

Damm straight, I'm already tall enough at only 6'6", don't want to be 6'10" like Bonz! You have my sympathies there sir. Folks can see from my photo that I posted in the luggage rack thread that my legs need room to stretch out, don't see how you do it on your stock machine?

T.C.

[Bonz]

6'11", but who's counting...

On the SG my knees have quite a bend in them with my feet going back to the pegs. I don't enjoy riding it is much the last couple years compared to when I first got it. I picked up that second SG that is in pristine shape with engine guards and highway pegs. I enjoy that much more.

[Schming]

You think I didn't try everything possible on 3 separate engines and 3 separate sets of carbs to eliminate it?

Probably Shaft Seals