Here's the story guys. I'm running a completely stock 99 Scrambler 400. I know a guy in town who has a 95 Scrambler 400 with boysen reed valves and an Aaen pipe. He came over to my house today so we could do some testing, and the results- I beat him! I was rather surprised myself. From a rolling start I can take him by about one four wheeler length over a 1000 foot long stretch.
After riding his Scrambler, I felt as if it has a strong take off, but it seems to lose power in the mid range and on top end. I've heard from mechanics that pipes can hurt your mid range and top end due to the fact they rob a lot of torque from the engine, perhaps this is true?? Could the fact that I have the new and improved concentric drive system affect things as well? Let me know your thoughts, I'm expecting to get a lot of feedback on this post considering a lot of you out there have modified Sports and Scramblers.

Mitch
99 Scrambler 400
97 Xpress 300

 

I would agree with your thinking as far as the new concentric drive system is concerned. It seems to be much more efficient.

RoostKing.

 

Aaen does make two different pipes, and your comment about the strong take off leads me to believe that he is running the low-end pipe (at the sacrifice of some top-end). Some minor clutch tuning mon your friends ATV might make a difference.

The Boyesen cage would also contribute to the better throttle response, but not neceassarily add much more HP.

Stock HP ratings should be nearly identical for both machines (36).



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Jerry Goodman '99 400L, '98 TBlazer

 

Mitch,

A brand new 99 quite possibly may be the faster bike.

It has all new parts, the engine is tight, all the bearings are new, and nothing has had a chance to get worn.

When you change anything on the engine, there needs to be adjustments to the clutching to handle the different power characteristics.

Your machine in it's stock form, should have everything dialed in right. Perhaps your friend needs to adjust the clutching to match the increased power.


Then maybe he can keep up to you!



RM

 

The bike may be running lean if it lacks top end or it could be rich if the filter is dirty on top. It will blubber is it is too rich and loose power if it is too lean. The tightness of the rear clutch will alter the top end by not allowing a complete shiftout. So it will not reach top gear ratio. A too tight rear clutch will also cause the motor to run at an excessive rpm possible above the peak power curve.

 

Absolutly correct Losi. After installing my 15.5:1 HPD billet head (w/girdle kit), I found my top end a bit off. Of course the new head has 10lbs more compression (195lbs comp.), but after talking with Darrell at HPD he thought my driven clutch might be too tight, and to try a softer setting. Jetting was not the culprit in this case, as my plug looks good.

I'm in the middle of it now, you know how working with these clutches can be. I'll find out here in a week or two if everything is back to normal.

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Jerry Goodman '99 400L, '98 TBlazer

 

I agree with some of you. If all he has is the pipe with out the correct clutch adjustment and/or correct jetting, it can easily make him slower than stock. If you don't have the tools to do it and can't find the exact clutch kit for the pipe owned, trial and error then takes the plate. A really good idea is to run at a 1/8 mile asphault drag strip about 5 - 10 runs. Take the average time, change something and try it again. It's gotta work!

WillieB - '99 Scrambler 500 - 10.6 @ 58mph (stock) in the 1/8th (660ft) asphault

[This message has been edited by Willie B (edited 09-08-1999).]

[This message has been edited by Willie B (edited 09-08-1999).]

[This message has been edited by Willie B (edited 09-08-1999).]