JETTING PROBLEMS?

[skemp]

No, I am only using the Dynojet needle, I lost all the Dynojet jets and my stock needle. You know how it goes when mom cleans the garage? She doesn't mean any harm, but stuff always ends up missing. It was okay because she bought me more main jets, and I am going to buy a new stock needle as well.

I am running 100 octane Av Gas, my step dad hauls it. I might try some pump 93 octane and see how that goes. I will also try putting it on reserve. This is weird, because when I added just the K&N filter and modified my airbox, I had it jetted perfectly at a 160 dynojet main. When I added the pipe, I began to have problems. I can feel that something isn't right, but the visual evidence (plug) isn't there.

EDIT: I will also look at my gas tank, sometimes we get dead bugs in our gas cans, so I usually try to strain it through something, or use the can with a screen in the spout.

Thanks for the suggestions!!

Jetting can be very difficult given the way you're approaching it. Plug reading has become unreliable given newer gas additives and longer life plugs.

Another (and safer) way to jet your machine is to "over-jet" it. The point is to make your machine run too rich - it'll give you a reference point.

First, you have to test if your machine is already running rich (with the 180 in it).

Put the machine in 2nd gear, get rolling enough so the machine isn't quite lugging, then roll on the throttle. Hold it wide open til it either (A) skips, blubbers, cuts out (can't miss it) OR (B) you've reached the top of the revs without the above symtoms occuring.

If you get A, then you're too rich on the main.

Else, if you get B, then run to your dealership and pick up a 182, 185, 188, 190. Retest with the 190 in. If you get A, drop to a 188 and retest.

Continue to do this until you achieve B. Then, drop back one more - you should be perfect then.

If 190 isn't high enough, go get more!

Although 180 does appear a bit high, only YOUR machine knows what it wants.

This is basically a fail-safe method, you will see results.

What to do with all the extra jets? Just return them, most dealers are happy to take back the unneeded sizes. Or if you're like me, you'll keep em, never know when the next engine mod will come along!

I've performed this jetting technique countless times - it is much easier and more effective. Plus, you won't have to burn your fingers trying to get the darn plug out!


Hope this helps,
ogre

[NVR2L8]

Here's my opinion... Guy660R and Ogre mentioned something that I ran into when jetting my 400EX, and it seems as though you've encountered the same problem--the detergent additives in the fuel you're using are keeping the plug clean no matter how rich you jet. Although I have no experience in running AV gas, I would venture to say it has quite a bit of additives to keep aircraft engines running clean, as the higher in altitude you go the leaner your mixture needs to be. Follow my logic? Anyway, I ran into the same problem trying to do plug reads...always read white...as the gas here in California is loaded with additives due to state EPA regulations. It wasn't until after my 416cc mods that I started running a 50/50 mix of 111 leaded race gas and 92 octane premium, and now when I read the plug it shows a nice light brown color. Must be the lead in the race fuel...

My advice is to re-jet using Ogre's advice. Start with the largest main you have and ensure it's rich by running at WOT and noticing a blubbering condition, and then work down just until that condition goes away. At this point you still may be a tad rich, but your motor will run a little cooler and will last longer.

NVR2L8 -

I agree with you, as soon as the blubbering goes away - it isn't a bad idea to stop there. The engine will run cooler.

When I installed my cam, however, I noticed quite a bit of carbon on the piston dome (rejetted previously for pipe, piston).

At that time, I was dropping mains til it stopped blubbering.

Now I drop it one more size down after the blubbering ceases. That's why I mentioned in the previous post to go down one size more.

Either way though, everything should turn out great.

Oh, and by the way, even after jetting with this method, my plug still reads grey - yet I know it's borderline rich. Goes to show that plug reading really doesn't work very well.

PS - I usually run 91-93 octane - NVR2L8 may be onto something with the leaded gas giving color to the plug. Using 91-93 octane, all I EVER see is white, grey, or black!

ogre

[skemp]

You guys are great! I am definetely going to get some pump 93 octane, I asked my boss at the gas station I work at if there are a lot of additives and my step dad who hauls gas and they both said the normal pump gas shouldn't have too many additives.

After that, if I still get no color, I will try ogre's method. Sounds like a good way to do it.

Oh yeah, I discovered something that made me wonder if I had found the problem, I took off my seat and noticed the carb was tilted probably 20 degrees to the right. I think when I last had the gas tank off, I put it back on and twisted the throttle arm and made the carb crooked. I fixed that and looked very closely at the carb and intake boots, and I also discovered that the bottom of the intake manifold on the motor was tucked under a bit into the carb. I am sure both these things would affect something.

I think it is a lot of things all mixed together, and I need to get some good gas, try the machine after I corrected those problems, try ogre's method (if need be) and report back within a few days when I don't work.

Thanks you guys so much for all the help you have given me.

[tinner]

Last year before I did any serious mods I just had a K&N filter/outerwear (w/lid),and FMF MegaMax.My jetting was 160 which was probably a shade rich because I had the stock lid and my stock needle was raised one notch.I would try the 162 and raise the needle up one notch from stock.Also I would try the 93 octane and that will probably help with the plug reading.I also live in Wisconsin so elevation should be pretty close.Good luck

[nakomis0]

When I ran 104 and 110 octane in my almost stock bike the plug was always white, because it burned so hot. Now I hear running higher octane will actualy lower your HP. Now i just run 93 or 94. So if your running 100 octane, than thats a good start changing the gas like ya said.

[Wheelie]

The AV gas is the reason your plug is white, it's not burning lean, it's burning clean!! Contrary to most beliefs the higher octane fuel will give you MORE power and COOLER running. I've run pump gas, AV gas, and Race fuel in my quad numerous times and pump gas sucks once you burn the good stuff a few times.

[4punksdad]

I recently experienced the same problem.

I am running a stock filter with a combo of different airbox mods, and a modified stock exhaust...........

stock jetting is a 148........I went to a 150 and a 155 and I am still burning white........I was going to go to a 160 & higher, but after reading this I might not.

The Washington DC area has been said to have alot of blended fuels which may be why I am running such a clean looking plug.

My old plug looked carbon fouled when I removed it for my plug tests. The old plug had been in the bike since before I modified the airbox & it might have been running rich to begin with.

I will wait awhile & check it again to see if I get any color after a few rides.

[Razorback]

Leo - this should probably be moved to the "best of" forum at some point; a lot of good information for people who have jetting questions.