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Discussion Starter #1
hey guys. i ran into a little set back. heres the story: i was racing my friend one night and we went at it. i pinned the throttle in 6th for about 10-15 second and the bike acted like it ran out of gas. i knew something was up. i slowed to a stop and tried to restart it but there was zippo compression. i took it apart and this is what i found. i was running a perfect 32:1 ratio using redline racing oil and regular 87 octane gas, the jet size is stock for the 85 250 i think its a 21 jet, i also have a powerhead on it i dont know what the dome size is or whatever. i had a head gasket blow a few weeks back and i replaced it that day. and my sister took it out with her friends and the expansion chamber came undone. i dont know how long it was ran like that. i tightened it up and ran just fine for about 30 before it lost compression.. ANY IDEAS?? im going to get it rebuilt but i dont want to have the same problem i had before..
 

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87 octane isn't enough octane for a stock engine. if you raised the compression at all, it gets worse. it probably detonated a hole in the piston. how much compression did it have before the problem? i would also have the squish band fixed on the cylinder head.
 

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Discussion Starter #3
idk what the compression was before. it ran just fine before. the cylinder is scored from the piston im planing on getting it bored and honed and possibly ported and polished
 

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definitely get the squish band checked and corrected on the cylinder head. atleast run 91 octane in it if stock compression.
 

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Discussion Starter #5
it did have a slight knock but it was only at a certain rpm. could that be a cause?? i talked to some other people and they said that all suzukis did that...
 

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there's alot of things that can make that noise, but i'd guess it was detonating. do you have the timing set at factory or did you have it advanced? that would make it a little bit worse on the octane required also.
 

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Discussion Starter #7
i didnt do anything to the timing. i didnt even know you could set it.. the manual says that you cant set it. and i was thinking that it was detonating. so does that mean i would have to retard the timing or advance it?
 

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you can move the stator plate, there is a mark on the plate and the case that you line up for the stock setting. alot of guys try advancing it to get more low end out of it, but you gotta match the entire setup for it all to work properly.
 

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Discussion Starter #11
no i didnt do anything to the timing. could this also be caused by reeds? too much room between the reed cage and the reeds themselves?
 

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i don't think so, i'm thinking you were running too low of octane and it detonated, and you were balls out and it melted the piston. the lt's are really prone to detonation because of the squish band and multiple other things like jetting, timing etc. etc.
 

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Discussion Starter #15
and yes, the carb is off an 85 and the engine is an 88. well it looks like i found my problem.. the cylinder looks like its going to have to be bored 10 over... easily. when i get done with all that, which jet size should i use?
 

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an 85 carb is only a 32mm mikuni while the 87 and up use a 34mm stock. thats probably choking it up a little bit also. surely you could find a good used 34mm somewhere.
 

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Discussion Starter #18
so there is too much clearence in the squish band, it will detonate.. and do you think i could jus fatten up the main jet?
 

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you'll have to measure the squish band when you put it all back together if i remember correctly around .040 is close and you will need to see where your at right now on the jets and how much compression the engine has when put back together also
 
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