Jetting Trouble Continued...

[maxthrottle]

OK, I put the DynoJet 155 main and needle in my 400EX.
I've got a Yoshi slip on exhaust, and a new K&N airfilter with outerwear...no holes in the air box.
I set the air screw at 3 1/2 turn out.
The engines starts great and idles fine. I haven't ridden it yet just playing with the throttle in the garage. As soon as I get to 3/4 to wide open throttle the engine winds up and then sputters. I've held the throttle wide open and have had some backfiring with an occasional 2" yellow flame out the Yoshi.
I tried the same thing with the air box cover removed, the hesitation at wide open throttle is still there but not quite as severe, does this mean the jet is too rich? Should I go down to the 150? How does the stock 146 equate to DynoJet sizes?
Do you think this will go away when the quad is ridden and there is a load on the engine or does it matter?
Any ideas?

[Leo]

I'd love to help you out, but I'm not really sure how the dynojet #'s translate over to Keihn numbers..

Anyone know?

Leo

[400exBro]

i think they are the same ....
Bro

[MadcapEX]

If you are just playing in the garage I assume it is in neutral and you are running against the rev limiter..You cannot tune an engine in neutral,ride it then tune it,you will find it much easier.:cool:

[maxthrottle]

I guess I should ride it to check it out completely. But I'll have to wait for the weekend. I'm thinking I'm too rich with the 155 in that its slightly better w/ the air box top removed. I'm hesitant to put holes in there...ruins the waterproofing.
Maybe Honda will come out with a laptop mapable, fuel injected quad and we toss this 100 year old carb technology!

[Glamis400ex]

I was told this by someone. Every time you mess with the intake or exhaust, you need to rejet up 1 size for each mod. EXAMPLE: Removing the airbox lid only....up 1 size, put on a K&N AND remove airbox lid....go up 2 sizes. If you add those 2 items and even put a pipe on....now you go up 3 sizes. Make sense?

Every mod you do go up 1 main jet size.

Mine is this....
DMC full pipe
K&N filter
choke removed
airbox lid removed
snorkel removed........I'm at a 160 main, and it runs great.....

Worked for me..Hope this helps

Glamis