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Author Topic: Build mostly done...shes running! WOW!  (Read 1972 times)

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Offline Vishnuatepork

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Build mostly done...shes running! WOW!
« on: July 11, 2010, 02:16:31 AM »
I got a call from the shop today.

"....Alan, you better come on down, its about your bike.....click"

I was sh*tting bricks, after a miscalculation with my  transmission shafts, and having to split the cases a 2nd time, I was worried.   Last I had seen the build was Thursday, the heads were waiting to go on.  I was worried the custom pistons from CP were going to be an issue.  Maybe the cams...too much lift???? Dunno..shrug

I arrive, and my mechanic was all like...you tell him.  ...sheepishly walks away, gets the keys, and starts her up. Very easy very fast start...WOW.

It happened so much I wasnt even able to savor it.

I almost cried.

So heres the tech question.  While blipping the trottle we heard some pinging..slight but there at around 3k 4k rpm
 I know the tech specs of the manual state the advance is
"
5   degrees btdc <1650rpm
30 degrees btdc >3500rpm (USA)
5   degrees btdc <1625rpm
35 degrees btdc >3250rpm (swiss)
5   degrees btdc <1625rpm
32 degrees btdc > 3750rpm (all others)
"


I have new pistons, 12:1 up from 10:1.
Mega cycle cams (shouldnt affect timing, for the sake of this question).
Some transmission work and ported heads.

Its carburated. (before I forget its a 1990 Suzuki VX 800, same engine as the intruder)

My thinking is that the a) gas is old. Its the same gas in the bottom of the tank from when I dropped it off on March 23rd. Old 87 pump gas. b) Although I dont have the pod filters or the exhaust on I yet, I think it may be lean (or at least carbs may be a touch less than clean) ....or at least a lean condition would contribute to a pre ignition issue.

Thought comments???

I wanted to know if there is anywhere I would find an online primer for setting timing advances, as I have a programmable ignition module I am going to install.

Cheers!
Alan

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suzuki vx800, 41mm FCR, shrink ported head, mega cycle cam, singh grooved head, custom headers, Supertapp exhaust, Ignitech ignition module, vs1400 drive hub, nology coils, magnecor wires, 12:1 cp pistons, carillo rods

Offline Cajun Kid

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Re: Build mostly done...shes running! WOW!
« Reply #1 on: July 11, 2010, 10:35:17 AM »
First off,,, I would drain that old pump gas,,, and at 12 to 1 I would never use 87 octane,,,  92 or 93 premium pump gas is barely enough.. I would use some 100 race gas or at least fresh premium pump gas and some octane booster.

Good luck.

Charles
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Offline 57 ranchwagon

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Re: Build mostly done...shes running! WOW!
« Reply #2 on: July 11, 2010, 10:42:46 AM »
I'm not much of a motorcycle mechanic but a car engine will knock and ping like crazy on 87 octane with 12:1 if it has any timing in it at all defiantly time for some 100+ octane gas.
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Offline Constant Kinetics

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Re: Build mostly done...shes running! WOW!
« Reply #3 on: July 19, 2010, 06:32:13 PM »
Timing won't fix all of it, though it will help. Get the octane up and use leaded fuel if you can find it.
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