Power on the main jet

[chef1366]

There is something else wrong.
That motor should pull to redline with those DJ 160s with no problem.
I'd check out valve clearance (may already of damaged valves) or ignition. I've seen poor ignitions do the same thing as with zero clearance on the valves.
Edit: could also be from leaky intake boots/o-rings

[Oliverstrother]

Valve clearances all within spec, but on the tight side. Book says 30-80microns is the spec.

Yeah, i heard about the leaky boot rings before, I took one off and it looked night perfect. not crumbled/cracked etc.

I could replace them all anyway, know a good supplier?

Thing is the problem isn't the whole running range, and its very very good on anything except the main jet.

Yeah, poor ignition will retard the top end, but it does gets a good spark, and has a new R/R, battery and stator.

At the minute, I"m sold on:
- Main jets too small, as the plugs look lean after 5mins on main jet. Order some 165's.
- Cracked boot seals, maybe. Cheap to replace so worth doing to eliminate as a cause.
- recheck valve clearances. Easy and simple to do. (and I have a new gasket waiting to be used.)

[chef1366]

When you put a jet larger than a 150 mikuni (160 dynojet) in a 650 it will not be lean.
I don't even have 150s in my fire breathing 1100.
If your valve clearance is good I would replace the intake O-rings.
The ignition will not retard the timing but be weak and put the fire out. The plugs will look lean by being washed out with gas.

http://www.cycleorings.com/

[tom203]

That 160 sure sounds like overkill even factoring in your oddball pods. So it won't go 60 mph in fifth- will it go 40 mph in third?? Or are you hitting some wall at 5000 rpm? How about going downhill (less load)-is it happier?

[Oliverstrother]

Hey, thanks for the input all.

Thanks for the reference point on the jets for the 1100 fire breather.

Yes it will go 40mph in third easily. The only wall I hit is around 9k rpm, under heavy load perhaps in 3rd gear or higher. It kind of goes 8k, 8.5k, 8k, 8.5k, 9k, 8.5k, 9k then kind of top out there.

It was happily zing up to 12k rpm in first or neutral. I'll check to see if will do this in second on the way home tonight.

Sorry, didn't mean poor ignition would retard the timing, just retard the performance.

I'm trying to get a video on the go, to show what's happening.

New O rings on their way. At least that will be one potential cause eliminated.

[tom203]

I am just trying to rule out the ignitor as the problem and you did!
12k rpm in first?? I missed a shift the other day going from 3 to 4- tach appeared to hit 10 k, I had visions about spitting valve shims, so I took it easy after that.

[wymple]

I must be missing something here. Stock main jets are 110. There is no way I can see that you are running 160 MAIN jets. 130 would be a big increase over stock. Are you playing with the wrong stuff?

[Oliverstrother]

dyno jet kits come with two options 155s and 160s.

Fuel flows throughout the jet based on the size and the pressure difference across it. Changing pods and exhausts etc, change the pressure differential so the size has to be changed to compensate.

Right now its running 160s, as recommended by dynejet, The plug looks as though its running lean after a highway run at full power.

http://youtu.be/m_13l3Zs4ao

heres a video of the power performance, it struggles at high rpm under load and kind of surges.

[chef1366]

Put larger main jets in it.
I hope it fixes your problem.
Remember that DJ mains are not the same as the Mikuni mains.
Did your kit include the brass inserts for the main air jet?

[tom203]

"....and its very very good on anything except the main jet."

"Yes it will go 40mph in third easily. The only wall I hit is around 9k rpm, under heavy load perhaps in 3rd gear or higher. It kind of goes 8k, 8.5k, 8k, 8.5k, 9k, 8.5k, 9k then kind of top out there.

Main jet, needle or airflow thru those odd dual pods- vacuum pistons have to open wide and be steady at increased loading.

[Oliverstrother]

Cheers fellas, I guess I'll have to go back to dyno jet for some larger DJ's. I had no idea they were different. If only it were simple. Eh?

[GSX1000E]

I am with Chef that something is missing in your formula. Most probably intake manifold O-rings or that air jet. Anyway, Dynojet 160=150 Mikuni. To help your stumbling block, I would go to a Dynojet 166 or Mikuni 155 main jet arrangement.
With pods and stock exhaust, I only needed 120 Mikuni (128 Dynojet) main jets on a 650 at Sea level.

[Oliverstrother]

Hey fellas,

Spoke to the guys at dyne jet who suggested i check the movement of the slides and test the performance without the air filters on.

I check the carb slides and cylinder 1 felt like it had some kind of obstruction, nothing serious, but certainly not smooth. I dismantled it and didn't find any damage. After reassembling it moved just as smooth as all the rest.

Performance without the air filters is much improved, but the problem is still there. Is this indicative of anything?

heres a video for those interested. https://www.youtube.com/watch?v=mdMg...ature=youtu.be


Cheers,

Oliver.

[tom203]

So letting more air in (filters removed), performance is "much improved" implies to me that your main jet is oversize for your filter setup.

[Oliverstrother]

Bang on.

Slapped in the dj155's the kit came with and it feels better. Although I haven't had chance to take it out properly.

Will try this today. And let you guys know how it goes.

Interestingly the dynojey guys mentioned that spark plug colour tuning is harder to do these day due to the additives in the fuel.