M600 -97 problem after rejetting

sjostedt · April 24, 2012, 11:34:43 AM

Hi,
I've rejetted my 600 monster with a factory pro jet kit. K&N pod filters and BOS competition slipon are installed aswell. I've come to the point where the bike runs really good when it's fully warmed up but doesn't really work that smooth while still cold. I've got the #140 main jet installed, the needles are on the 3rd clip and the mixture screws are 6(!?) turns out. I didn't recieve new pilot jets with the jet kit should i order a bigger size? Well to my problem;
When cold, the bike surges a bit and doesn't respond that well if i juggle with the throttle, there's also some pops from the exhaust when accelerating . The idle works just fine. It's around 4000 rpm where it seems to have the most problems. When i checked the spark plugs after a short ride the top cylinder was a bit dry fouled and the day after that it started on just one cylinder and it took about 200 meters before it came to its senses and the other cylinder started working. What should I do? It works good when fully warmed up but it seems I'm missing something. I'll change the spark plugs and richen the needle one clip but should i have to worry about the main jet?

ducpainter · April 24, 2012, 12:15:27 PM

The mixture being out 6 turns suggests you need bigger pilot jets. It also could be the problem at 4K if it occurs at very low throttle openings.

What do you mean by 'dry' fouled?

sjostedt · April 24, 2012, 01:03:30 PM

Dry fouled as in fouled and dry?

isn't that what you call wet / dry fouled? Or is it just "fouled"^^ Haven't got the hang of the english engine terms quite yet.

So you think a bigger pilot jet could fix it all? And it could be around 1/4 of throttle opening when it surges/backfires. I'll have to think about that next time i ride.

ducpainter · April 24, 2012, 01:11:36 PM

Quote from: sjostedt on April 24, 2012, 01:03:30 PM
Dry fouled as in fouled and dry? isn't that what you call wet / dry fouled? Or is it just "fouled"^^ Haven't got the hang of the english engine terms quite yet.

So you think a bigger pilot jet could fix it all? And it could be around 1/4 of throttle opening when it surges/backfires. I'll have to think about that next time i ride.

Your English is fine. It's us that come up with these silly descriptions.

That isn't fouled. It's sooty.

At 1/4 throttle you should be into the needle, but the pilot and main are still both affecting the running. The 6 turns out should be corrected. That seems like a lot

How many miles on the bike? Have the needle jets ever been replaced?

Is the jet kit you bought specifically for a 600?

sjostedt · April 24, 2012, 01:39:06 PM

Yes the kit is specifically for the 600 bought from the factory pro website. The needles, main jets, emulsion tubes (from FP aswell), slide springs and the pilot jets have been changed. The pilot jets were the same size tough. The 6 turns was necessary for the bike to work properly(set when fully warmed up), didn't have a choice since i didn't have any other pilot jets. I'll have to visit the local duc shop and ask for a pilot jet i guess. I'm not quite sure about the main jet, it pulls strong at high rpm but i haven't really been able to try it out that much and it didn't work properly last season when i bought it so i don't really have a good reference.
27k miles almost exactly.
The carbs are evenly synced just a couple of days ago.

ducpainter · April 24, 2012, 02:37:11 PM

The jet kit probably assumes you'll run an open airbox.

The pods may need bigger jets and a different needle setting.

What main jet was in there stock?

Typically when you jet an engine you get the main jet right first and work down because the main jet affects everything.

If you can do some high rpm/high speed runs and check plugs without letting it idle, you can tell if you're close.

Then adjust the needle if you have to.

When you get those done you can decide if you need a different pilot jet.

sjostedt · April 24, 2012, 02:52:45 PM

Yes i know the main jet is supposed to be corrected first but since it worked more or less i didn't bother at first

the main jets were # 135 stock and now i've got #140 so i've stepped it up one step.

ducpainter · April 24, 2012, 02:55:08 PM

Quote from: sjostedt on April 24, 2012, 02:52:45 PM
Yes i know the main jet is supposed to be corrected first but since it worked more or less i didn't bother at first the main jets were # 135 stock and now i've got #140 so i've stepped it up one step.

Is that the only size the kit came with?

When I jetted my 900 the jets that came with the kit were too small because of the amount I drilled my air box lid.

You should verify that the main works better than 'more or less'.

sjostedt · April 24, 2012, 10:28:14 PM

Quote from: ducpainter on April 24, 2012, 02:55:08 PM
Is that the only size the kit came with?

It came with a #140 and #145

I'm going for a bit of a longer drive this weekend which will give me opportunity to try the main jets. Would the best way to do this just to check the spark plugs after a high rpm run or should some other technique be used, like comparing when it pulls harder, when cold vs warm?

ducpainter · April 25, 2012, 03:03:05 AM

Do a high rpm high speed run and hit the kill switch. Pull the plugs and see how they look.

I'd think with pods you'd need the larger jets...at least.

sjostedt · April 26, 2012, 05:59:35 AM

I were out testing today. Going 70 mph on 3rd gear just to get the high revs

I took a few pictures on the spark plugs, and what i can see there doesn't seem to be that much of a problem with the main jets?

I was going on about 7000 rpm and then hit the kill switch and let the bike roll into the gas station where i took these pictures.

ducpainter · April 26, 2012, 11:32:29 AM

As long as that was at wide open throttle I could live with that.

That's one variable eliminated.

Since you're having trouble in the mid rpm/throttle area I'd raise the needle a notch and see if the popping and stumbling diminish.

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M600 -97 problem after rejetting