6k stumble

[planedick]

After setting valve clearance my bike ran great when I went for a hot run on the freeway, then I had an intermittent loss of two cylinders on the way back. After some looking and discussion with the Whiz I found a pickup wire was rubbing on the rotating timing disc and I corrected that problem and that fixed that and then I decided to do a carb synch and idle mix adjust. Now I have a great running engine right up to 6 grand, but anything further isn't happening. Just stumbles and won't go beyond 6 grand. I made no changes to the carbs except for synch and idle adjust. What went wrong?

[planedick]

Playing with needles

Since I had always seen lean conditions when I read the plugs, I decided to try different needle positions. They were in the middle position so I first tried raising them by putting the clip in the bottom position. Short test ride showed extreme rich and couldn't even get to 5000 rpm, so I then moved them to the second from top. This time the test went better, got to 7000 before stumbling, so I guess the next move is the top position.

[egsols]

What size jets are you running?

[egsols]

Like DiverRay said in another post, double check your float bowls in case the main jet was loose and turned out. I have heard of that happening to a few.

[planedick]

Jets

Stock jets as all is stock, airbox and exhaust. I think 137
Also it's not just one cylinder, it's all, so I don't think it's a loose jet unless they all came loose.

[egsols]

Timing okay? Vaccum advance working okay?

[planedick]

Check

Took off the timing mechanism, checked and lubed the centrifugal advance, checked all else, timing OK, good spark, both vacuum and mechanical advance working OK. I'm really at a loss to explain all this. It was a little noisey, so I decided to do a valve adjust as I found one exhaust at .012". When I finished that I went for a ride and it hauled a**. Got on the freeway and run it up real good and when I exited I experienced a loss of cylinders while waiting at a signal. Limped a little to get off the road and it started running good again. I found a pickup wire rubbing the timing plate and had worn the insulation off and was shorting out. It was an easy fix to move the wire tape up the insulation and properly position it to prevent it happening again. Running smooth again, so I went for a test ride. Now for some odd reason it won't go over 5000 rpm without crapping out. Up to that point everything was great, 0 to 5000 rpm runs strong and steady???? I checked the plugs and they were black and sooty, so I moved the needle to the bottom position and tried it again....DUH I moved them the wrong way. So then I moved them to the 2nd slot down from the top and test ride showed much improvement and the plugs are cleaning up nicely, but it still won't excellerate above 6000 rpm without going at it slowly. Scratching my head so much the thin spot is really getting bald. LOL

Oh, I forgot to mention, after valve adjust cold compression was 120 strait accross and affter the first run while still hot compression was 140,130,135,140. I just wanted to do it hot to be sure I haden't got any clearances too close.

[planedick]

Next

I have since moved the clip to the top slot and tested it, but it still won't excellerate past 7000????? I guess the next step is put the washer on top.

[Crazcnuk]

I have the same problem.

After doing all the service work to the carbs, I got it to idle great, run good from the start, great through the middle, but in 4th gear it tops out at 7,000rpm and in 5th it won't go past 5,000rpm, unless I wind 4th out first.

It has NO roll on power at highway speed. I can crack the throttle wide open at 70-mph and I get out accelerated by everything, including school buses.

I have ordered a set of 115 mains (my carbs are 110's) becuase I have an aftermarket 4-2 exhaust and K&N air filter.

Will see how that works.

As for your needle changes I don't think the needle jet is doing anything at 7,000. You should be fully on the mains.

[planedick]

I found out

that I can't put the washer above the clip as the spring ID is larger than the clip. Looks like I will be pulling carbs and rejetting. I just wish I knew why. I tried setting the timing a little ahead and it helped a little, but I don't think I want to leave it there. I wonder if raising the fuel level in the bowl will help.

[trbig]

My bike used to do what you guys describe when I put the cheap pod filters on that restricted some of the jets on the carb bell. Could there have been some sort of obstruction or something causing the air filter to be stopped up?

Just another thought is all.. you guys are looking at jetting when there may just be an air intake problem?

Tod

[TopCatGr58]

Hey Dick,

Okay, it ran great after your synching UNTIL you lost the cylinders due to the PU coil wires, which sooted your plugs. Have you tried putting in NEW PLUGS? Also, are you sure your repair is holding, folks have repaired the PU wires just to have them break again, but they didn't find it for a while because they were "JUST FIXED", so it couldn't be that, and went thru a lot of carb tuning loops!!

Are you also sure you're getting enough fuel? Are the vacuum lines going to the petcocks intact, not leaking? Have you tried it on PRIME??

I was also going to suggest checking your snorkel, a fellow had dropped a socket down inside there and was having all sorts of air flow problems, TOD/TrBig just posted along the same lines!
T.C.

[planedick]

Hmmmm

Airbox restriction? I didn't check that, but I will when I go to the mancave. I was thinking about rejetting because everything is good except WOT. Up to 7 grand is OK, but after that is crap. I think today I will take the carbs off and do a carefull inspection. I just have been putting that off because it's such a PITA. The pickup wires weren't broken, just the insulation wore off in one spot and I don't have an ignition problem anymore. I have to get this sorted out or the trip to Yosemite is off.

[trbig]

TC touched on the other thing I was thinking. A kinked fuel line somewhere would do that also...


Tod

[planedick]

Lesson for the lazy man...

I tried everything I could think of that I could do without removing the carbs.... DUH Little voice in the backof my mind kept telling me to do that, but I was just too lazy and it cost me two days of anguish and wrenching. I found that the float height was way off. I had nver had these apart because it ran just fine when I got it. The floats were set at .875" instead of the .975" in the manual. I decided this morning I would remove the carbs and check 'em out. Took about 15 min to get 'em off and within an hour I had 'em back on. Another 30 min and had 'em synched and set the idle for the best rpm's. The test ride was great. Ran better than ever at all rpm's. I will definately remember this lesson and the next time I won't be so lazy. I could have been doing other things for those two days.....

Thanks all for the input....