A little background info...



I recently acquired an 01 Dyna T-Sport FXDXT. Apparently when it was bought new in 01 it had a 95" kit, shaved, ported, polished heads, cams, Fireball ignition, etc... but no actual proof of the work.

I had the bike "pre-inspected" at a reputable HD shop and also dyno'd. The bike pulled around 90hp and 100ft. lbs, so I'm pretty sure the motor work is correct.



The shop did mention that it would detonate if it was lug'd down low but other than that, it ran like a champ. Also during a compression test it pushed 220psi on each cylinder.

It's only ran on premium 91oct fuel or 93oct containing 10% ethanol.

After putting on 1000miles, I decided on playing with the ignition. I know the high compression is playing a tole as it hesitates to start and that hot of a motor isn't "streetable".

The ignition, model # 8-3160:



I spoke with S&S today to try and play around with it a bit, they didn't know a whole lot because apparently they bought Crane Cams and all of these ignitions are now obsolete. They pretty much just went over the instructions that I found online.

Available here: http://www.cranecams.com/uploads/ins...s/90003160.pdf

Does anyone have any experience with these?

Right now they only way it won't detonate is on the following set-up.

Mode : 1 (single spark pre-loaded tables)
Rear Cyl Offset : 0
Initial Timing : -5(minimum advance)
Advance Slope : 0(minimum advance)
Rev Limiter : 6200rpm

When I purchased it, it was the same minus...

Initial Timing : -4
Advance Slope : 1

It is a little better now, but I can still make it detonate if I whale on it below 2500rpm. I tried some Octane booster in today's tank and it did seem to improve a little more.

I ride pretty aggressively and usually never under 3000rpm, but it's still not right. I can stand it straight up and carry a wheelie easily, but if I catch myself off guard I dont want to run the risk of detonation causing engine damage.

It looks like I'm going to have to take it in over winter and straighten it out, maybe add some decompression valves and see what cams are in it.

I have a feeling they're the main culprit... I bet it's too short of a cam with not enough overlap that's driving the compression up.

It's hard to really say anything right now without knowing whats on the inside, but I just want to make the most out of the rest of this riding season.

Anyone have any pointers or suggestions on how to deal with this now? Or even what to look for down the road once I get this thing apart?

I'm thinking it might be more cost effective if the cams are the issue to just install a set of S&S easy start cams... that way I dont have to mess with machining the heads.

 

Hopefully some Harley mechs will jump in, but I would guess your corrected compression ratio(ccp) is really high. If you pull your top end apart and cc those heads along with finding out what cams you have, then you will be able to make some good decisions. I would be thinking about reducing the ccp either by better matched cams or increasing the size of the combustion area. I have zero input on that ignition, good luck!

The recommended high end for cranking pressure is around 190 psi, so your 220 psi is way up there! I would be talking to a Harley mech that is recommended near where you live.