Hi guys, this might be my first post here but i've been reading these threads for some time and couldnt find what i was looking for with the search tool. A week or so ago i took apart my carbs and soaked them in some carb cleaner solution and put them back together, replaced my gaskets and reed gaskets and put it back together. I noticed when i started the sled that it wasnt running quite right, so i pulled the coils one at a time to see which cylinders were good and bad. it turns out that the cylinder closest to the clutch was getting spark and fuel but not running well. the machine wouldnt idle on it but if i gave it gas it would run. so i checked the compression on each cylinder and the one closest to the clutch was about 10-15 psi less and lost compression faster than the others. i realize its most likely time to do a top end rebuild, but my question is if i run it this season, will it do enough damage that ill have to send it out to get re-honed? do you guys think im good for this season or should i just invest in a wiseco rebuild kit and do it before i get out? Thanks!
Devilin AblueDress!
New member
I would suspect you have a bigger problem than worn out rings/top end. 10-15 lbs lower and losing compression faster.....I would at least get a little flash light with the bendy head on it. Pull that plug and stick the flash light down in side to get a good look at the piston/cylinder. When you had reeds out did you take a gander at the back side of piston? You could pull the manifold off and look at the front of it as well. The year before last the girlfreinds 2000 sxr 700 burn down the center cylinder. ODD part...had within 3 lbs compression as the other 2, leak down test revealed it held little to nothing. Whipeing out the crank when the piston lets go or the junks floating around in the bottom would concern me more than ruining the cylinder......cylinders are cheap....cranks not so much!
fi .rst off take the carbs back off and clean the pilots out with compressed air! see how it runs then. if still having problems pull the head and check .. if rings and piston checks out ..replace head gaskets.if that still dont fix your problem then you prolly got bad crank seal and must be replaced good luck!
well i ended up ordering the wiseco kit anyways just to do a top end in case. when i took the head, manifold, and between the cylinder and crank gaskets, i noticed they were all doubled and i was wondering if this is uncommon. i also looked into the carbs a bit more and noticed what i think is under jetting. the main jet is at 147.5 and the pilot is 52.5. i bought this sled used and never looked into it very much. i bought it with bender triples on it and assumed it had the right jetting. after reading around it seemed like my main would be set at 152 and the pilot where it is. im confused why someone would change the pilot so much and the main so little. i think the damage to the piston and gasket was from being too lean, so i hope rejetting is the main problem
staggs65
Moderator
the double base gasket sounds like the "poor man's porting" it raises the port timing. be careful though because it usually goes hand in hand with machining the head or running less layers of the head gasket to get compression back. If you choose to go back to a single base gasket you will need to figure out what you need to do up top to maintain a safe compression ratio
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How would I go about doing that? I'm pretty sure it was stock pistons and rings so I don't know why the previous owner would do that. If I set everything back to stock and use stock size pistons will that be enough?
staggs65
Moderator
it has to do with the head. if the head wasnt decked then everything could go back to stock. you'd either have to cc the head or put it back together stock and check the squish with some solder.
Devilin AblueDress!
New member
Plucan said:
Trail or race porting is actually machineing ports in cylinderto change intake/exhaust routing/timing. The "poor man" trick is to double stack the base gasket, which effective changes timing as well. Raising the cylinder also rasies head, raising head creates a much larger combustion chamber/lowering compression. To get this back guys can/will modify head or top of cylinder,or gasket. Staggs concern was if you go back to single layer base you will need to check your squish (search squish). Basically if you dont have enough room between top of piston and head at top dead center causing detonation or piston may actually hit head.
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staggs65
Moderator
what he said,
sorry for being confusing, I scan just about every thread here and in my rush to get through them my thoughts dont always transfer well to print. lol
sorry for being confusing, I scan just about every thread here and in my rush to get through them my thoughts dont always transfer well to print. lol
Do you think the double gasket may have been related to running 147.5 main jets with bender pipes?
staggs65
Moderator
possibly. if he doubled the base and didnt do anything up top to get compression back it would certainly appear to run rich. its all speculation until you figure out exactly what you're dealing with
I believe the reason it wasn't running right to begin with was that it was running too lean. And I wasn't getting the correct compression on the pto side. The head gasket was also doubled, and the exhaust gaskets too
staggs65
Moderator
I'm not 100% up on the redheads. but if they are like the Viper there are actually 3 layers to the stock head gasket. If you had 2 single layers of head gasket then it sounds like he removed 1 layer.
Devilin AblueDress!
New member
The head gasket "out of the box" so to speak brand new should have 2 gaskets with a metal plate between them, all of it hel together with rivets. Your saying doubled head gaskets. Are there 4 layers of gasket with 2 layers of metal dividers? When you took it apart it came apart in two peices with multiple layers riveted?
It's basically like 2 gaskets that separated pretty easily when I pulled them apart. Are the rivets on the outside edge of the gasket? Because there are holes on the outside that look like they may have been drilled out for rivets. Later today I will take some photos of the gaskets and upload them
For a Bender piped "unported" 700 Sx[from setup sheet]
0-3500', 0 - 35F
Pilot Jet = 52.5
Fuel Screw = 1.5
Main Jet = 150
Jet Needle= Pto #3, Centre#4, Mag#3
PREMIUM FUEL ONLY
0-3500', 0 - 35F
Pilot Jet = 52.5
Fuel Screw = 1.5
Main Jet = 150
Jet Needle= Pto #3, Centre#4, Mag#3
PREMIUM FUEL ONLY
thanks for the setup bob, i think im gonna go with that. it was either that or 152 main jets. anyways i have some pictures. i think it will help you guys visualize what im working with and help me understand better what might have been wrong.
Attachments
sleddineinar
VIP Member
There would be no gain in separating or thinning the exhaust gasket.