79 550 Tuning woes

[Guest]

Ok. Ive been having a bunch of trouble getting the jetting right for a while now. Bought the bike with a debaffled wide open kerker 4-1 and no air box so i went straight to pods without having the chance to get a baseline.

I followed the pods/pipe link when i did the initial jet with no luck.

VM22s btw. Stock main was 80 pilot was 15. According to the sticky i should have been at 87.5 main and 17.5 pilot. 1 clip up on needle. With those settings i had no luck. Bike was rich at mid and lean on wot chop test.

Went back to middle position on needle, up to a 92. Needle was fine wot was rich. Dropped to 90 main and now the bike bogs bad at anything more than 1/8-1/4 throttle. To the point where it wont move under its own power.

Floats arw at 24mm, pilot #2 is stock 50, pilot is 17.5 with 1 turn out on fuel screw, air screw is at 1.75 turns out, needle in middle and main at 90. Valves all in spec, new plugs, wires, caps, points, condensors.

With all that i tried moving the needle both ways to no avail, tried +/- 1 main size and its a no go
It runs the best as it is.

Now if i hold it wot it will eventually power through the bog/stumble and just rocket away like a bat outta hell.

Could this be caused by a poor stator or bad coils failing under load? I know the battery is bad but it will kick start with no issues.

Oh and it fouls plug #4 a lot. I will change it and it will run fine for 1-2 mins while riding then fouls and craps out.

So wjy would just #4 be fouling? Im answering my own question here. Its pointing at the coils going bad. Just want some opinions.

[tom203]

"Now if i hold it wot it will eventually power through the bog/stumble and just rocket away like a bat outta hell. ...


So wjy would just #4 be fouling? Im answering my own question here. Its pointing at the coils going bad. Just want some opinions."

Since it "rockets away" eventually, your coils are unlikely the culprit here. But check your timing advancer to make sure it ain't sticking.

[tkent02]

Not sure how familiar you are with the first generation 550s. Trying to get a strong middle range out of a 550 isn't going to happen. It has none no matter how it's tuned. The rocketing away is pretty much all it has.

[hampshirehog]

FWIW, I've done quite a few of these and always left the pilot jets alone and raised the needle one position. I can't remember what I changed the mains to but you're about right. Bit of fiddling with the fuel and air screws also required but nothing drastic.

[tkent02]

What he said, raising the needle a half position using washers might be perfect. I would think bigger on the main too but it's hard to tell from here.

[KickerATW]

Thanks all. I just got em out for spring. Well see how it goes this year.