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Discussion Starter #1
hi all i have a 93 vmax4 it seems to foul the plugs every time i start it cold can i use br8es plugs instead of br9es i think part of the problem is that its been so warm this season i always use 93 oct. gas just to be safe so do you think it would hurt to use a hotter plug on the warm days and switch back to cooler plugs on cold days i burn 93 oct. because wiseco does not make the pistons for the 880 big bore anymore and i dont want to burn it down im jetted a little fat but as i said its better fat than burnt any suggestions?
 

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I do not know anyone that has used a hotter plug on the V-4, I would not do it, it will be hotter at WOT and that will eat a piston. Check and clean carb. I'd adjust the needle hight before I'd use a hotter plug.
 

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The way i understand it 93 octane doesnt burn as hot as 87, have you tried that?

also i would raise your clip on the needle one slot before changing plugs also.

Zagg
 

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plug fouling is a syptom of somthing wrong,out of adj.,pluged, worn. a hotter plug is a bandaid instead of a fix & might cause problems up top (just as toydoc said).
The fuel octain idea is agreat one if the compression hasn't been increased (are those higher comp. pistons, heads been shaved?)
How does it idle when its warm? make sure you don't have a choke plunger sticking. try turning the fuel off before turning the engine off & then turning the fuel back on after starting it(if this model has a petcock), if this works you could have a leaking inlet needle. if not and it idles poorly or comes off idle poorly clean the pilots,if they're not pluged decrease your float hight.
have you checked your compression?
 

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Discussion Starter #5
the engine is brand new less than 500 miles so i dont think is compression or leaking seal i am not real good with carbs is it difficult to adjust the needle height ? the thing that i cant figure out is if i start the sled let it warm up change the plugs it will run perfect all day then the next morning if its real cold it will foul the plugs on say 2 cylinders this engine is realy tight and when its cold it may take as may as 11 pulls before it starts could it be that its just not broken in yet if its kind of warm sey 30f degrees it will start and run fine may only take 3 pulls
 

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are the cyl.s that are fouling the same each time?
what was done on the rebuild, top end, bearings , seals?
who did the work? did they adj. & sync. the carbs?
any other symtoms at all?
just for the #### of it, after pulling about half as many times as it takes to start it pull the plugs & see if there already wet.
 

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Discussion Starter #7
its not always the same cylinders the engine was completely redone by hauck motorsports they are one of the best at making modifcations to the mighty vmax4 or any other yam for that fact they indexed and welded the crank and i assume the did not reuse the old seals i have some new plugs so i am going to try what you said and see what happens
 

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Corvette its because of the crappy warm weather.  My 600 twin has had it happen to me twice this year and my mach did it once.  It happens when you drive it in the warm and shut it down and re-start it in the cold.  The combustion chamber has all this moisture in it from the last time it was run and it shorts out the plugs causing them not to fire.  

It did it to me on Ngk, Splitfire, And now I am trying bosch and had good success but the weather was a steady cold so maybe thats why.
 

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Discussion Starter #9
i kinda thought the warm temps had something to do with it as cold air is denser than warm quess i will wait till it gets cold for a few days and then check it out thanks
 
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