Still stumbling

[slip]

Ok, my bike is still stumbling a little in the mid range of throttle. Things done so far are:

Rebuilt VM29 carbs
Cleaned K&N Pods
Installed new coils and plug boots

One thing I did do that might be a problem is, I put the needle clip in the second position from the top. It was in the middle position. When I got it, it was running rich. But that could have been from a number of other things, not nessesarily the jetting.

But there is something else that might be causing a problem too, and that is, I only get about 12.8 VDC at the battery while revving it to about 7k rpms. I think my stator is putting out about 60 VAC at that rpm. In my mind, low primary voltage is going to equate to lower secondary voltage, and hence weaker spark! What does the collective minds of the gurus think???

[TheCafeKid]

Ok, my bike is still stumbling a little in the mid range of throttle. Things done so far are:

Rebuilt VM29 carbs
Cleaned K&N Pods
Installed new coils and plug boots

One thing I did do that might be a problem is, I put the needle clip in the second position from the top. It was in the middle position. When I got it, it was running rich. But that could have been from a number of other things, not nessesarily the jetting.

But there is something else that might be causing a problem too, and that is, I only get about 12.8 VDC at the battery while revving it to about 7k rpms. I think my stator is putting out about 60 VAC at that rpm. In my mind, low primary voltage is going to equate to lower secondary voltage, and hence weaker spark! What does the collective minds of the gurus think???

12.8 at 7K means you have charging problems to say the least. either your stator, or your RR are shot, or you have some corrosion going on in the wiring... Id suggest tending to that before you move on with the carbs.. Secondly, without doing plug chops in the necessary throttle positions, you truely have no idea where your carbs are rich or lean. The needle may have nothing to do with your problem, but the stumbling is most surely due to your moving the clip.. put it back, fix the charging issues, and then start with the carbs. Unless you are getting AT LEAST 12.7v AT THE COILS, you arent getting a good spark for sure.. and that will only compound your problems..

[slip]

12.8 at 7K means you have charging problems to say the least. either your stator, or your RR are shot, or you have some corrosion going on in the wiring... Id suggest tending to that before you move on with the carbs.. Secondly, without doing plug chops in the necessary throttle positions, you truely have no idea where your carbs are rich or lean. The needle may have nothing to do with your problem, but the stumbling is most surely due to your moving the clip.. put it back, fix the charging issues, and then start with the carbs. Unless you are getting AT LEAST 12.7v AT THE COILS, you arent getting a good spark for sure.. and that will only compound your problems..

I did the voltage check with the ground and power leads to the regulator, and saw that there was not a significant voltage drop, so I suspect my wiring out to the rr is good. I did replace some bullet connectors as well as running a separate ground lead from the rr mounting plate. But I do suspect my stator might be bad. I should just probably get a new one.

[slip]

Well, I put the clips back in the middle position, and it is running much much better, but not quite there. But it is fine in the midrange now. I mean I can feel the monster within, but it misses some in the higher RPM's. I do think is is electrics now, and not jetting. So I guess I will order a Stator, as I don't think it is the RR. The stator just will not put out more than 60VAC no matter how high I rev it.

[slip]

Geesh, now I don't think it is the stator. I pulled the plugs, and while the #1 and #2 looked nice and clean with a slight brown on the white insulator on the inside, numbers 3 and 4 were fouled. Number three was wet, while 4 was full of soot. Do you guys think that maybe these 2 spark plugs are bad??

[slip]

One of the plugs just would not clean up, so I purchased a new set. I am going to remove the carbs and do a bench sync first, something I really didn't do after cleaning and rebuilding them, I just did a quick check. This time I will go through the proper procedure. Then hopefully after a test run, all will be good. Wow, I have never had to really troubleshoot an improperly running motor before to this extent. but then on the other hand, I have never owned a motorcycle that was 31 years old!!

[TheCafeKid]

Geesh, now I don't think it is the stator. I pulled the plugs, and while the #1 and #2 looked nice and clean with a slight brown on the white insulator on the inside, numbers 3 and 4 were fouled. Number three was wet, while 4 was full of soot. Do you guys think that maybe these 2 spark plugs are bad??

Could be the plugs, but perhaps you should check the plug caps resistance, (when is the last time youve replaced them actually?) I would say the coils could be at fault but 3 and 4 arent paired on the same coil so i dont think its that.. Wet with gas and you have consistant spark says to me that the air isnt getting there, maybe turn the idle air screw another half turn? black and sooty says you're getting spark, fuel, and air, but too MUCH fuel... Plugs RARELY are the culprit, but it wouldnt hurt to eliminate them from the equation. Gap correct also?

[TheCafeKid]

One of the plugs just would not clean up, so I purchased a new set. I am going to remove the carbs and do a bench sync first, something I really didn't do after cleaning and rebuilding them, I just did a quick check. This time I will go through the proper procedure. Then hopefully after a test run, all will be good. Wow, I have never had to really troubleshoot an improperly running motor before to this extent. but then on the other hand, I have never owned a motorcycle that was 31 years old!!

Ahhh yes, Bench sync is NECESSARY. I bet that is likely part of your problem with 3 and 4...Now, if i remember correctly, on the VMs there is no "master" carb, they can be individually set..so you'll want a baseline...A paper clip is an awesome gauge for this actually...

[slip]

Ahhh yes, Bench sync is NECESSARY. I bet that is likely part of your problem with 3 and 4...Now, if i remember correctly, on the VMs there is no "master" carb, they can be individually set..so you'll want a baseline...A paper clip is an awesome gauge for this actually...

Great, thanks for the info. In otherwords, I then will be able to use any carb as my baseline????

[slip]

Could be the plugs, but perhaps you should check the plug caps resistance, (when is the last time youve replaced them actually?) I would say the coils could be at fault but 3 and 4 arent paired on the same coil so i dont think its that.. Wet with gas and you have consistant spark says to me that the air isnt getting there, maybe turn the idle air screw another half turn? black and sooty says you're getting spark, fuel, and air, but too MUCH fuel... Plugs RARELY are the culprit, but it wouldnt hurt to eliminate them from the equation. Gap correct also?

I only have the air screws turned out 1 turn on all 4 carbies. The coils and plug caps are brand new.

[TheCafeKid]

I only have the air screws turned out 1 turn on all 4 carbies. The coils and plug caps are brand new.

They need to be turned out another half turn or so at least. Especially 3 and 4, try setting them all at 1 & 1/2 turns out.

[TheCafeKid]

Great, thanks for the info. In otherwords, I then will be able to use any carb as my baseline????

Yes, use the paperclip to gauge the opening on the slide. Stick it under the slide, the width of the paperclip should be your baseline.

[slip]

Yes, use the paperclip to gauge the opening on the slide. Stick it under the slide, the width of the paperclip should be your baseline.

Thanks, I will do that tonight.

[slip]

They need to be turned out another half turn or so at least. Especially 3 and 4, try setting them all at 1 & 1/2 turns out.

Thanks again.