I had my first ride over the weekend on my Scrambler 400 4x4 after fitting an RCR air box mod, Delta V Force 2 Reeds and an HPD reed spacer. I had rejetted the carb from a 260 to 270 Main Jet.

When I was just hitting full noise (man it gets there quick now!) the engine would die completely. Like I had run out of gas or something. It would be back after about a second, and be hauling a$$ like nothing had happened, but as soon as I got close to top again, it would die again. Very frustrating when you are trying to get around the outside of a Banshee in a high speed slippery turn.

Can anyone help me by telling me what is happening, and how to fix it?

 

I will take a guess. If you do not have a pipe on your bike then I think you are jetted to rich. I have a pipe and the airbox mod and I run a 270 in the dead of winter a 260 in spring and fall with a 250 in summer. I would go back to the 260 and see if it runs better.

KD

 

Kevin

I have a HPD Trail Pipe, and a custom muffler based on the HPD one. Also a Cool Head, Wiseco Piston and K&N Filter. Most riding is at sea level.

 

I had the same exact problem & I checked fuel line, reeds, piston/rings, plug etc everything 3 times & found nothing. I gave up, sent it to my mechaninc & he's had it for 3 weeks & he cant find the problem either. He thinks it' electrical now. My friend had a similar probelem on his LT250 Suzuki & it was a dirty electrical connection.
Jim Maloney 98 400 Scrambler
http://photos.yahoo.com/jim400scram

 

You only run on your main jet when you are at full throttle. With that setup it sounds about right with the main jet. Could be a few things. Check all your connections to make sure there is abslutely no air leak in the carb boot, reed spacer, etc. Make sure the reeds are not loose. Adjust the needle e-clip one step richer, or possibly two, depending which step you are at right now. I've seen certain cases like this when you are on the extreme end of the needle, it's better to go one step richer/leaner with a different needle and get the clip closer to center. You mentioned you have a cool head??? Are you running the correct fuel for the engine compression? What type of carb?

 

Jack

I have the Pro Design Cool Head with the stock size dome (45cc). I alos have the High compression dome (43cc), but not fitted yet. I use 96 unleaded gas (we only have 91 or 96 unleaded to choose from here).

I am running the stock carb with a 6CEY6 neelde from a 98 sport (as recomended by HPD for the pipe) on the middle position with the spacer (1/2 a clip).

I have the new reeds set in the low tension position. I understood the you need to be running a high compression engine to run the reeds in the high tension setting.

I will be taking the reeds out again and installiing them making sure that everything is tight, seated properly and there are no air leaks. I think I will also move the needle up one clip, but the mid runs sweet, it is only the absolute top that cuts out.

 

Check your tank vent for blockage or kinking .

 

Good call.

 

Also check all the carb vent tubes. It's real easy to get one laying against the pipe and it will melt shut causing some strange problems. I had one like that a while back. It ran great until about the 3rd run and it would cut out the same way.

 

Thanks Jack

I had the carb and reeds out last night. Everything looked OK, but I think I might have had the breather on the bottom of the carb stuck between the carb and the rubber block on the gear case that the carb rests on.

I also checked all the other breather hoses and they are OK - no blockages and no kinks.

Do you know when I should run the reeds in the High Tension position?