I have now decided to not do a 104mm piston (leaves very little piston skirt), and neither a 103mm piston (reports of unreliability)..
So I am going with Kev and dl700's (Dan's) advice, and I am going with a 102mm piston, a CP.

The engine is going to the engine builder on Saturday, so a strip down will start soon....I will send my crank to Dan at High Desert Dyno, so he can have a look at making a Stroker Crank for the XT's.......

Dynojet are still working on the rev-limiter, and this is my build spec (so far! I may change!!)

High Desert Dyno/ Cuervo Racing Gas flowed and ported Cylinder Head with
Larger Valves (+1 mm)
Uprated Valve Springs and guides
High Desert Dyno 5050 Camshaft
Rev limiter
102mm CP 11.5:1 Piston (686cc)
Nikasil Cylinder Barrel, bored to suit piston
High Desert Dyno +3mm Throttle Body

my existing mods are:
DNA Stage 3 Airbox
Power Commander
Carbon Cans Exhaust

My aim is: Not to lose any power at all in the lower revs,hopefully gain a fraction, and to have a driveable bike, that will pull through all the revs.

You will be fine, with that set up its going to fly.

I am very interested in the stroker crank, once Daniel can see one, hopefully he will be able to make them up for us as a straight bolt in crank.

Sounds like a good package. Could you keep an account of the costs? Always interesting to see the price/power ratio.

(No problem if you don't want to)

Thanks Kev for your comment...

I have a feeling I may lose 1-2 hp around 3500 rpm...but thats not a really big deal, but totally against my original plans....(no laughing Kev!!! lol)

I think the 103mm bore would have offset any small losses with the 5050 cam, but a well built/spec'd 102mm may even be better! We'll see....


As for the Stroker crank, I hope there will be some interest from other forum members, in tuning their bikes....or from people who wouldn't consider buying an XT before, who were maybe looking at Husky/KTM, or from MT-03/Derbi Mulhacen/Aprilia Pegaso etc. owners ..........

It would be so much better if also a 105mm bore was a more cost effective/less labour intensive project......

you will get the whole price...when i have finally got there....including shipping etc.......no problem....

What I will say is,,,so far a DNA Stage 3 Airbox is highly recommended as an easy hp/responsive power improver.........and it looks dead sexy too...and exhausts should be a second priority if you are after a performance mod...

As you know I am trying to build a cheap fast XT at low costs.

A stroker crank, standard 100mm XT660 piston, re decked cylinder with a compression ratio of 11.5:1, stage 2 hot cam, ported head & hope to get around 60HP. We will have to wait & see.

I have all the parts lined up using a Raptor Hot Rod +5mm stroker crank, Raptor flywheel & stator. I will wait to see what Daniel says when he sees the XT660 crank before I do anything.

Yes, I like your idea.......a good project from behind the scenes, Kev...

All being well, Dan should have the crank in about 2 weeks, Kev....I haven't bothered with forwarding you anything Kev, as its just been sorting out the logistical (shipping) bits.....but you will be the first to know when the Crank is finally sent off.....

Of course, your shipping charges are totally different to ours, so I hope the overall package works out reasonably economical on the shipping front. I think it would be interesting for us two to compare the costs of our mods, for other forum members..

That's no problem, we will wait to see what Daniel says when he sees the XT crank.

Just remember all my modding & machining is labour free, or at mates rates.

you are going to be alot cheaper than me.....I wish the other Kev was my next door neighbour.....