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Postby Matt-itude » 12:21 am Apr 29 2006

The possible loss I was talking about was way up high in rpm. But right up to that point (which is past where you can reasonably shift anyways) I would say no loss maybe even a little more power. I can dial more timing in also because of altitude compensation. Lots of my rides easily exceed 8500ft. I may turn the timing back just to see if I notice any differences. But first Ill have to get bored with all this other stuff (jetting). I keep thinking when I do my top end Ill send the head in and have it done. When you say detriment do you mean power or piston life? I am assuming power.
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Postby Rhodester » 01:31 am May 01 2006

Sorry, I've been crazy busy.

I had the cylinder base shaved to indeed lower port height to gain bottom end along with a minor compression increase to still be able to run on pump gas. Remember, this was part of the experimental fixes I tried to help cure the bottom end hesitation I had when wicking it.

I haven't noticed any decrease in top end or resistance to rev out as much as it seemed to before the timing and cylinder mod were done.
On the ATK406 I used to have, it had a series of shims that were used instead of a head gasket. The difference in top end run out was quite noticeable between say 1 shim and 4 shims. It also made a significant difference in how snappy the bottom end throttle response was (or wasn't).

CC, I'm wondering how much of a factor lean jetting may have been in your engine self destructing. Was the jetting dialed in after the porting, but before the melt down??
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Postby canyncarvr » 10:53 am May 01 2006

Detriment question was in regard to performance.

re: '..I'm wondering how much of a factor lean jetting ..'

Lean jetting had not a thing to do with it (IMO and all that caveat). After the install of the ported/replated cylinder when the detonation problem started, I rejetted using not only a seat-of-the-pants dyno, but a bracketing method. I was on both sides of 'correct'...too rich and too lean. I've 'leaned' toward lean a couple of times (with some other changes made) in an attempt to resolve my dripping rear fender. I'm slowly becoming convinced that ski is's the USChrome plate job that's the source of the drips in my bike.

An interesting aside: My bike idle has been less than terrific since the port job, too. Idle speed is very low, raising the slide doesn't make much if any difference. It's not a problem unless the bike idles a LOT combined with no-load ops other places in the throttle range (like putting around doing course flagging and such). There was an 'all-of-a-sudden' change last spring. Idle was completely different! Adjustable, solid, a bit higher RPM. I realized after fixing the KIPS drum lately..that the better idle situation occurred exactly the same time the drum blew out!


Rhodester: You've mentioned your long journey over the hesitation problem..I didn't realize cylinder changes were part of it.

Can you give an outline of what it was you were trying to resolve..what did and did not work...what the final result is/was? Maybe in a separate thread? Kind of an FYI sort of thing? I'd like to read it.

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