High end bogging problem.....

[Sandy]

The easiest way to confirm whether it's coils or not would be the swap in a set of known good coils to test. If you've got a spare set around or can borrow a set the would be great. There is still a possibility that it is carburation but symptoms do seem to be pointing towards electrical. It would be too bad to fork out the money for new coils and still have the problem. I'm not sure of proper testing methods for coils but if you checked resistance between the 12V and ground connectors the readings should be the same on both sets, as well as checking the plug wire to ground the readings should be the same. Do this with the coils unplugged of course. This could be a start, although the way it's behaving they could both check out good. Maybe somebody else has a good way to check the coils.

[semerm]

similiar problem

I have a gs850 that i bought with pods on it. I had EXACTLY the same problem only mine would only get 5000 rpm. I yanked the pods out, installed the factory airbox and now it runs like a different machine and I get 8000 rpm easily. My bet is it is the airbox/jetting. Please let us know what you determine it is.

[morbidphil0622]

Is your petcock vaccum operated? If so, try changing the settings to reserve and if that doesnt help run it on prime and see if that helps. I have had a problem with this on a bike that I had once before. I swapped everything electrical, coils, ignition box, plugs, wires, etc.. it was expensive and did not work, but hey at least I got it all out of the way. If your petcock isn't vaccum operated then just shoot me the finger... Jason

[BadBillyB]

Alrighty. About 6 months ago I changed the head gasket so while I was at it I went ahead and went through the top end. Basically all I did was clean the head up, make sure everything was alright, and put it back together. I did not do any valve job or anything, just cleaned everything up and put it back together (I vaccum checked all the valves and they were all sealing up great). After I put it all back together this problem began.

This would make me highly suspect that you might have the cam chain on wrong. One tooth off on one sprocket can wreak havoc on your tuning. Re-check your valve timing........BadBillyB

[Chris Daniel]

Well, after digging a little deeper into the wiring and coils I found 3 things.

#1. The coils only have 9.7 volts going to them (with the bike not running).
#2. The number 1 plug wire right at the coil has a rather large crack in it facing the fuel tank. I was able to stick my mulitmeter probe into the crack and the other probe at the end of the plug wire and get an ohm reading........so the core of the wire is exposed. This is also the plug that I have intermittent problems with it fouling out.
#3. I pulled the plugs and 1-4, the plugs are black except for the very tip of the porcelin and the tip of the electrode, which are very dark grey. Now, 2-3 the porcelin is white and the electrode is light grey.

Now would either of these cause my problem?

If I decide to go with the dyna coils do I need to 3.0 OHM green ones?
Is it OK to run the wires with no resistor in them with a plug with no resistor in them (I am assuming that a D8EA NGK is a non resistor plug)?
In other words, do I have to have some type of resistor, be it the plug or the cap?

About the cam chain, that has been a passing thought. However, I checked and double checked when I installed it. As far as I could tell, and according to my climers manual, I was spot on with the cam timing. I am not ruling that out, I just want to cover all other bases before I go pulling the cam cover off again.

Also, I replaced the stock petcock with a "racing" petcock (no reserve) from Pingel, along with nice pretty yellow fuel line and a quick disconnect fitting......which has come in quite handy with diagnosing this problem.

Thanks for everyones help.

[Billy Ricks]

Don't bother with Dynas, check Ebay for some coils of of a GSXR, Bandit, or Katana. From about 2000 on GSXRs got individual coils in each plug cap. You can usually pick them up for about $30 on Ebay. These are a little steep, but if you watch you can get them cheaper. http://cgi.ebay.com/ebaymotors/05-Su...spagenameZWDVW

[DSchuess]

Another similar problem

I got my bike (1980 GS550L) last September but didn't start riding it extensively until this spring. When I got it, the plastic connector from the single air cleaner opening to the four carbs was missing. I rode it this way briefly, around the neighberhood less than 3 miles per ride, and it ran fine. I finally installed the part over the winter and it seemed fine at first but on a recent outing with a local bike club (about 45 to 50 riders on 150 mile trip with one Yamaha, one new Suzuki and my 26year old bike being the only 3 non-Harleys, and my bike made it the whole way and was by far the oldest there) I found out that I couldn't go over about 3000 RPM which limited me to about 55-60 MPH. When I first noticed this problem I tried removing the air filter briefly and this did not help. Since then I have completely disassembled and cleaned the carbs and everything seemed to be in order with them, after this I was able to hit about 65 MPH and around 4000 RPM. I checked the manifolds and can find no leaks. I have sync'ed the carbs twice and it doesn't help. Plug 2 is the worst looking of the plugs and #1 isn't much better but #3 and 4 look pretty good generally. From reading previous posts it sounds like one coil controls 1 and 4 and the other is on 2 and 3, if this is correct is it possible that they were attached out of order on my bike? I am going to check the coils in general next but any further advice would be greatly appreciated. Aside from side covers, this bike is bone stock and, as far as I know, was all original when I bought it. Also, it only has 15,000 miles on it but I am not sure how long it sat idle at various points in it's life but I don't think it has been ridden frequently in a long time. Thanks again everyone.

[DSchuess]

Follow up on above.

Well, after writing that post I went out and checked my coils. I guess I should learn to trust my instincts as sure enough the 1/4 coil is bad. I reads about 4 Ohms and drops about 9 Volts. I first checked spark between each plug wire and noticed that #4 seemed weak, then putting the Fluke meter on the coil confirmed it. Also, my wires are all numbered so as long as they are correct, I answered my own question about the possibility of the boots being switched. Hopefully I am well on my way to getting my bike in proper running condition.