Spark Breaking Down at High RPM

[suzuki-newfie]

Hi All,

I have a problem with my bike at higher RPMs and I'm hoping someone can help.

To provide some history, the bike is Canadian and originally had an ignitor box for the electronic ignition. Ignitor failed and I switched to points and condensors (realize this is a step back in technology - am considering the Dyna S).

The problem I get is that it seems like the spark on cylinders 1-4 is breaking down at 7000RPM and above. The reason I think the spark is breaking down is because it starts to backfire, but will still go to the red line eventually. The reason I think it's 1-4 versus 2-3 is that when I hook up my timing light, it give a good strobe right to the red line when connected to 2-3. The strobe is very intermittent when connected to 1-4 when RPM increases.

I originally thought it was the coil so I got a used one but it didn't seem to make a difference. I noticed a slight improvement when I re-adjusted the points and timing, but not enough to stop the backfiring.

My first hunch is that I might have a bad set of points on the 1-4 side. Note that the bike did work ok at high RPMs last year. I wanted to get a 2nd opinion(s) prior to springing for the Dyna S.

Thanks,
Suzuki Newfie

[oldschoolorange]

What kind of bike do you have? I have an ignitor, pickup and coils for an 83 550 I may sell

[suzuki-newfie]

Thanks oldschoolorange.

Can anyone else give input on my diagnostics?

Thanks.

[tfb]

When did you last change the spark plugs?

The few times I've had high rpm mis-firing, it's been a fresh set of plugs that's done the trick.

Best to start there, and then start wondering about the more expensive items...

[suzuki-newfie]

There is a brand new set of plugs in it now - any other ideas?

[earlfor]

When you tried the used coil, did you use the spark plug caps that came on the used coil, or did you swap the plug caps from your original coil. If you used the same plug caps on both coils, the problem may be the old caps.
If you used different caps on the two coils and the result was the same, then I would suspect your pointset needs replacing.

Earl

[bonanzadave]

When you tried the used coil, did you use the spark plug caps that came on the used coil, or did you swap the plug caps from your original coil. If you used the same plug caps on both coils, the problem may be the old caps.
If you used different caps on the two coils and the result was the same, then I would suspect your pointset needs replacing.

Earl

Or both sets of plug caps are shot. Cheap easy fix...go get a set of new NGK plug caps. Cut off the old caps to reveal clean wire and screw on the new caps.

[suzuki-newfie]

When I replaced the coil, I did use the same old caps. I did measure and they do have the prescribed amount of resistance. I'll replace the all the caps first and then look at the points (or finally make the jump to a Dyna S).

As I said previously, the points were a set that I swapped out from an older bike in favor of the electronic ignition. I don't know how old the points are (I'm guessing pretty old) and I'm not really sure now how I'm going to source points for the bike since I don't know what model and year the points came from.

Thanks for the help.

[earlfor]

OK then, lets look at it another way. Points were generally discontinued at the end of the 1979 model year. Your breaker plate will be 1979 or older. The breaker plate obviously fits a 550. hehehe
There are only two types of points. Single screw hold down ND (Nippondenso), or two screw hold down KD (Kokosan) Look at your pointsets to see if they are held to the breaker plate with one screw or two.
NOw, go to http://www.crc2onlinecatalog.com/
Points will be found under the electrical heading in the left margin.
Order a set of points for a 550 1977-79. Pick the single screw or dual screw type, whichever you need. :-)

Also, once you find out whether you need ND or KD points, you might PM me and let me know. I have some new points sets in my parts stuff (dont remember if theyre KD or ND at them moment though) and no longer have a bike that uses points, so if you can use them, I can let you have them for an "unbeatable" price. LOL



Earl

As I said previously, the points were a set that I swapped out from an older bike in favor of the electronic ignition. I don't know how old the points are (I'm guessing pretty old) and I'm not really sure now how I'm going to source points for the bike since I don't know what model and year the points came from.

Thanks for the help.

[suzuki-newfie]

Thanks Earl. I'll check the points style and send you a PM.:-D