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1,687 Posts
Discussion Starter #1 (Edited)
JohnyC recently set the ball rolling by fitting a Speedmaster 790 inlet cam to his Scrambler,
as per his thread:-

Ive now had the opportunity to carry on where he left off.
Johny sent me his cam when he’d gone as far as he wanted to go.
As we’d both carried out very similar intake mods, the only real difference between his bike and mine was the exhaust.
I have a very open Zard 2:1 system.

First I threw in the new cam with no other changes.
Initial testing showed that I’d totally transformed the bike!
As was also proved by Johny, the bike took off at about 5500 revs, straight to the limiter in all gears.
For the first time ever I shot straight up to 85, 100 and 110 mph in 3rd, 4th and top gears!!
The trade-off was a loss in that low/mid range grunt which makes the Scrambler what it is.

Dependent on your preferences/likes/dislikes/requirements this mod in itself may suffice in getting more out of the stock (very derated) Scram.
As long as the reduction in low-down torque is accepted.

I then went to the next stage and contacted Pieman about the Igniter mods which he carries out at
He raised the rev limit to 8500rpm and uploaded all five 270° 790cc maps to the igniter and also added extra advance to the 100% WOT map.
In the mean time I also slightly increased the main jetting up to 135’s from the 132.5’s I was running previously due to the A/F showing slightly lean.
Today I again tested the bike.

Result: Bloody unbelievable!!

The only similarity to the bike I had last week is that a photo would look the same!!
Ive regained the losses down low (below 5000 rpm) and now have a very lively sports-bike-like feel to the top end.
The performance is quite amazing in comparison to before, with revs rapidly attaining max in all gears with no hesitation.
Also the throttle response is immediate and both induction and exhaust tone completely changed.

I know, I know, it hasn’t been dyno’d so to some this will all mean little, but believe me the SOTP in this case is a very good indication!
Maybe one day I’ll find somewhere to plug it in and post the results as a post-script.

For those who may find the above improvements appealing:
Go for it!!


8,872 Posts
well did i call that one lol? I knew that cause i had been there and done that lol. Now put some good flat slide carbs and pod filters and it will be right from down low to red line.

1,687 Posts
Discussion Starter #6
Very interesting........
Are you going to leave it that way for awhile?
I certainly will, for the time being anyway. We'll see if the novelty wears off!
But I doubt it now that Pieman's re-map has recovered the majority of low/mid range,
I'm lovin' the more responsive top-end!

Well did i call that one lol?
.........Now put some good flat slide carbs and pod filters.......
You were never doubted Mike!
You're insight in the direction Im going is always appreciated.
Maybe hi-comp pistons next eh?! I'm on the case!! clarify that is with stock pistons & C/R, correct?
B02S4, yes thats correct. All stock (ish)
Usual airbox mods, plus a little extra, without actually removing it.
OEM pistons etc.
The only mechanical changed being the 790 inlet cam.
Oh, and a 17T front sprocket for added zip!!

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