Any time you change the stock exhaust to aftermarket you will usually run leaner and will need to have your carbs rejetted and then balanced. Check your spark plugs to confirm if it's running rich, black carbon look on the tips or white at the tip which means lean. When running correctly it should have a nice tan color on the tips. The strange thing about your description of how it runs, it sounds like your running rich sometimes and lean at others when it should be running consistently lean due to more air going into carbs because of better breathing from the aftermarket exhaust. I'd take it to a good dyno tuner and let them due the jetting for optimum performance.

 

Dyno



Thanks CP7
Checking the plugs is a simple enough task so I'll do that. I also checked up for a dyno tuner in my town and found motospeed Vasteras, who are a dynojet, dealer just down the road from where I work so I will be drooping by those guys

 

Sounds just like how my bike was. Your profile says you live in Sweden?

If it is a European bike, then replace the standard 17.5 pilot jets with 15. If they haven't been changed, also replace the float bowl needle valves.

My bike is much better after making those changes, but will still bog occasionally on a hot day when pulling away. Lowering the float level by 2 mm is also meant to help, but I haven't tried that myself.

 

Jets



Thanks NZ. with the other info I'm getting it's beginning to look like I need to renovate the carbs with new jets valves and seals. I'll do some research on the float setting also.

 

It appears to be an Akrapovic exhaust. You shouldn't need to re-jet with it. Are you sure you pulled the pilot jets and got them cleaned? It sounds like they're still plugged. The pilot jets are long and skinny and have a bunch of holes in the sides. The jet itself is super small and it's not easy to see if they are cleaned. You need to hold them up to the light to make sure you can see through them. If you pull the carbs again, remove the float bowls and flip the entire carb bank upside down. The highest part of the floats should be about 4.5 mm above the gasket surface.

Mark

 

Akrapovik



Thanks Mark

I looked up Akrapovik and you are right... That's some awesome bike knowledge you got there fella! so thanks for that
I remember the pilot jets you talked about mostly because they were a bitch to clean. I blew them out with compressed air as well as carb cleaner but was never sure if they were fully clean, it's hard to see.
I'll check them again and the float height. I'll drop by a tuning shop in my town first and see if there is a dyno jet kit available and go from there.

 

I have some info on setting up the float levels. If you can PM me your email, I'll send it to you.

 

Did you ever sort this out. I have the same problem. Mine is 1999 complete stock. Carbs rebuilt, new jets and needles.
After 5 miles on highway it bogs at stop lights. Need to slip clutch and bring rpms up to 4000+ to get rolling good. After 4-5 minutes at 30mph everything is fine again. High speed plug check show tan. Rechecked float height several times. Engine temp always remains between
84-92c. Suggestions?

 

I've had the same problem. A few questions.
Did you replace the float needle valves?
Just new needles, or needle jets as well?
Where is the clip on the needles?
Are the jets all standard? What size are the pilot jets?
How many turns out are the pilot screws?
How did you check the float levels?

 

carbs were recently done again with all new needle valves, seats, low speed and main jets, has Ivan's needle kit installed per his instructions. I forgot I did recently do the Ivan's airbus modification to it and install a lower temp cooling fan switch. before at high speed engine would run in the 105-108c temp range now stays in. the 84-92c range.

 

Do you know what size the pilot (low speed) jets are?

My bike would bog after waiting at the lights on a warm day, but going down a size on the pilot jets almost completely fixed it. I also found it was very sensitive to needle position and ended up using washers like those in the Ivans kit to adjust them down half a groove.

You could call Ivan as you've fitted his kit.

 

More on the Ivans kit. Apparently there are 2 types of needles. One for the stock filter and airbox and the other for race filters and the modded airbox.

I'd suggest a call to Ivan. I expect he'll have the answer.

 

you guys with stock setups are probably looking at the wrong end. Sounds more like the EXUP rusting out and not opening up.

 

That wasn't the problem on my bike.

 

I found my problem, wasn't float level, exup, needle position or anything along those lines. Rear brake. It looks like the brake fluid has never been changed. the pressure relief port on the rear master cylinder was partially blocked. On a long higher speed run enough friction on the disk was heating up the fluid expanding it. The relief port was not venting it back into the master cylinder. It was in turn applying more pressure to the pads. As long as I had the RPM's up I didn't notice it, but trying to come off a stop at low RPM's it manifested itself as boggling down, no power. Flushed the brake lines. Cleaned both master cylinders and slave cylinders. No more problem, and I've had a jump in gas mileage. I haven't had the bike very long and still learning the feel of the bike. The bad part of it is I remember we dealt with this type of problem freqently in the early 70's when hydraulic brakes were first becoming common on bikes. Changing and flush your brake fluid may help your good brakes work even better.

 

:lol :shake: :lol

On another note, where did the facepalm go? :rant:

 

Kangaroo. I guess I'm confused, why was is such an obvious solution to my problem? Im new to the bike so don't know the feel for the overall power it has. I did realize the preformance was lacking after hard run at low rpm's. I know the carbs on these bikes have given people a lot of grief. When in traffic it always isn't easy the test all the different systems. Your suggestion of a exup valve stuck closed would of had the opposite affect, It would have preformed good at lower rpm's but I wouldn't of been able to make sustained higher speed runs.

 

depends again on the difference between "how things should be" and "how things are." I don't know but I'm adding some food for additional thought having been around these bikes for the past 20 years. Like that one guy who had a sticking rear caliper as the cause of the engine "bogging."