Bigger than a 170 main on a 400ex??

I had posted asking for help before, thanks to those that replied.
link to my original post here, http://209.120.142.52/showthread.php?s=&threadid=20153

I am wondering if anyone out there has ever needed more than a 170 main?? right now I have a 38pj, 170mj, needle on 4th notch down.
Below is a recap of the results I have had so far.

The carb is stock. I have an alum airbox w/ no lid, UNI high flow multistage foam filter, and ground out the welds on the headpipe and gutted the spark arrestor. I have 87 octane gas, should I use 93? The weather is like 95 outside with 40% humidity.

First I raised the needle one notch and I can tell a big difference, it starts and idles easy when cold with no choke. Even on a hot summer day if the engine was cold id have to choke it a bit to get it running smooth.

So I figured if it started easy I’d remove the choke assy. and put in the 160, I ran 2 passes WOT, killed it and rolled to a stop. I pulled the plug and the porcelain is white which is too lean right?

I had forgot that I had 1 step hotter plug in so I put the stock plug in (DPR8Z) and changed from a 160 to a 165 and it is still white after a WOT run.

170 and plugs still white but mid throttle and idle the plug shows tan-chocolate brown. I went and rode it hard for a few minutes and the only thing is after I ran it WOT thru the gears up to 4th and let off the gas it popped thru the exhaust a little. The quad doesn’t seem to have any bogs or flat spots at all, if it wasn’t for the plug being white it’d be hard to tell anything is wrong.......except that one pop out the exhaust when I let off. I did a search for backfire and saw people describe the same thing and everyone responded that it was lean.....

I have ridden it and it certainly runs better. My cousin has a Raptor with Trailtech speedo and I seem to be running aprox 70 MPH, I have no idea how fast I was before the jetting…. also he doesn’t walk off and leave me in a race anymore.

[VegasEx'r]

I've got a 175 right now. I am still fine tunig the jetting w/ my new cam, so I don't know if it's right or not. I haven't checked the plug, but it feels right at WOT.

[Glamis400ex]

by all means son.......use 91-92 octane gas

Glamis

will get 92 octane gas. I checked the plug again and it was white after mid throttle also. I am gonna try the needle all the way up.

[Leo]

Originally posted by FastnFurious1
The carb is stock. I have an alum airbox w/ no lid, UNI high flow multistage foam filter, and ground out the welds on the headpipe and gutted the spark arrestor. I have 87 octane gas, should I use 93? The weather is like 95 outside with 40% humidity.

Yes :D I'd be running at least what's recomended in the owners manual.. (92 or 93 if memory serves)..

If your worried, you could always start bumping up the jet size and doing timed runs until it starts to drop off and or feel funny.. probalby the safest way to jet is go rich until it feels 'rich' then back off a size or two.. Mine's happy with a 162, but no two bikes are the same, and location / temp / altitude / etc can have a big impact on jeting..

Leo

[B@ckBoneBelgium]

In the HRC Manual from honda they suggest a 165 main , a 62 pilot and the needle Must be on the 3 thd place from the top ....

Running this setup now and I am very happy in te combo , 11.1 piston and the HRC Cam ..

Also do yourself a favor and buy the HRC needle ..BIG Difference

Order number 16012-NKK-000

Just give it a try

[skemp]

I have some experience in jetting, and to me, it sounds like the main is probably just fine. A 170 isn't too huge for a stock motor, but since you said it popped out the exhaust after you killed it, it sounds like maybe the 170 is too big. It may have left a bit too much unburned fuel in the combustion chamber, and it ignited through the exhaust when you hit the kill switch. Oh yeah, you are probably wondering about the plug color, huh? Well, first of all, run premium. Second, you will have to search far and wide to find pump gas that gives the same plug readings as yester-year. Most fuels now are oxygenated and they also have many detergents added to make them burn cleaner. Since you are seeing white no matter what, I can tell you that you aren't running lean, you are running clean. The gas is cleaning the carbon off the plug, so with this one, you will have to settle with feel, and not with the physical proof of the plug. I would go with a 165-168 main, 40 pilot, and needle in the 3rd position. This should not only run good, but also keep you on the safe side. I haven't seen anything but white on my plugs until recently since I am now running a 50/50 mix of 110/92 pump. The leaded fuel seems to let the plug get some color. Good luck!

Originally posted by skemp
since you said it popped out the exhaust after you killed it, it sounds like maybe the 170 is too big. It may have left a bit too much unburned fuel in the combustion chamber, and it ignited through the exhaust when you hit the kill switch.
it popped when I just let off the gas for a second, not when I killed it, it poped just a little and then I got back in it and it responded fine. It has only done that once.
thanks for the tip on the gas!

Originally posted by B@ckBoneBelgium
In the HRC Manual from honda they suggest a 165 main , a 62 pilot and the needle Must be on the 3 thd place from the top ....

Also do yourself a favor and buy the HRC needle ..BIG Difference

Order number 16012-NKK-000

A 62 pilot??:confused: do the HRC numbers match std keihin part numbers?

[400exRacerX]

I'm running a 195 main.:eek:

[B@ckBoneBelgium]

The HRC numbering is correct to the keihein , because the logo of keihein is on the pilot .....

Originally posted by 400exRacerX
I'm running a 195 main.:eek:

wow, well I shouldnt need that much since my motor is still stock, just open airbox and opened up the exhaust.

I still need to get the 40 pilot I think but I believe a 62 may be a bit high for mine.

also I just tried raisng the needle up another notch which is all the way up and it was missin out and sputtering at half throttle so I dropped it back down one notch, I am on the 4th down which from what I have read is where most everyone is running their stock needles.

Now that I know what the missing out and sputtering from being too rich feels like I can continue to jet up till I get it to do it on the top end.

[FullBore52]

hey norm, is that on a stock carb? Im not that much higher than you are norm at a 210 in a 39FCR...hmm...