Triumphrat

SMGray · 05-06-2008

I've got about 600 miles on the Scrambler and I've been careful with the break-in. It's been re-jetted and has the TOR pipes on it from new and it has run absolutely perfectly from day one.

However, I took it for a ride tonight and for the first time I really got on it. Previously, I have kept it below 55mph and ridden it easy throughout the break-in. Tonight I tromped on it and took it at full throttle to about 6,500 rpm. I noticed a little flat spot or slight miss right at the 5,000 rpm mark. I took it through three gears this way and had the flat spot or miss in each gear. She seamed to stumble her way to 6,000 rpm.

Normally, this won't be any problem because I don't ride my bikes hard and most likely will spend the vast majority of the time below 4,000 rpm. But I would like to know what the cause is.

I should state that this bike starts and idles perfectly with choke for only 10 seconds. After that it needs no choke from cold and never needs the choke when warm or slightly warm.

But I would like to know what causes the stumbling at 5,000 rpm. Any ideas?

mikeinva · 05-06-2008

sounds like its not the right main jets

Pokeyjoe · 05-07-2008

Quote:

Originally Posted by mikeinva

sounds like its not the right main jets

Or maybe you need a shim. What jets were put in it?

Malibu · 05-07-2008

yes indeed. With TORs and the stock airbox you should probably use 1 shim. If you swap out the paper filer with a uni filter, she'll have more power and not feel as choked, but then you'll probably also need to jet up to a 120. you should be running 115's if everything is stock, except the pipes. It's hard to say though, the airbox and snorkle keep it from getting that little extra umph at the top end. I aint suggesting anything, it's just that getting it perfect is pretty hard the way these come stock. I've tried and I know. Check out what size main jets you currently have. I used 115s and 120's with TORs and the stock airbox, and both were fine. Using the 120s allowed me to put in a UNI filter— and feel it immediately. I don't know what else they could have done.

SMGray · 05-07-2008

I don't know what jets were put in. The dealer did it before I took delivery and other than the flat spot at 5,000 rpm I haven't had any problem at all. I'm not going to worry about it. The bike runs so well otherwise that I'd hate to start fiddling with it and run into any other problems.

Pokeyjoe · 05-07-2008

Quote:

Originally Posted by SMGray

I don't know what jets were put in. The dealer did it before I took delivery and other than the flat spot at 5,000 rpm I haven't had any problem at all. I'm not going to worry about it. The bike runs so well otherwise that I'd hate to start fiddling with it and run into any other problems.

Adding a shim takes just a few minutes. Its very easy to do. You remove the gas tank and take off the top of each carb. If you don't like the result, take the shim back out and you're back where you were.

Malibu · 05-08-2008

I know the feeling. Mine had a BIG flat spot when I picked up my Scrambler the first time from someone that "fooled" with it—someone who should have known better. It took me a while to get the hang of doing my own jetting, but I'm glad I did.

SMGray · 05-08-2008

What all goes into adding a shim? My experience with carbs is limited to the old Amal concentrics so I obviously am not familer with what a "shim" is or how difficult it is to install. Are there any threads or sites that show a pic of what this is?

drlapo · 05-08-2008

i think the Jenk's Bolts website stil has a free tutorial on how to work on the carbs

Pokeyjoe · 05-08-2008

Jenks Bolts
^
The link. Page 4 shows a picture of the pieces that come out of the top (ignore the drill bit stuck in a hole). The needle sits in the white plastic piece under the spring. It just sits there. You pop it out, put a shim under it, and put it back. That drill bit is in a vacuum hole in the slide. Make sure the hole is facing the engine when you put it back together.