Pauljones
New member
I have owned my 98 srx700 for about 4 years now. It has 11 000 miles.
I keep my clutches in top condition (oil-lite brass bushings, new parts, everything very clean, and typically run a 8bu-10 set-up). I also have changed the gearing to 13 wide hyvo gears with a ratio of 23-39. My carbs are always spotless and I make sure my stock reeds are in top shape. I clean and adjust my powervalves at least once a season. I rebuilt my entire skid by fabricating brass bushings to significantly tighten everything up (way better weight transfer after fixing the skid).
The guys I ride with are constantly amazed at how fast my sled is. I would like to know if I am playing with fire since the top-end has never been touched. Is it just a matter of time till something goes? Would I notice a power increase if I did the top-end? The Yamaha parts would cost me about $600.00 and I would rather put the money towards another srx, but if I am playing with fire I will do the top-end. Do top-ends ever go due to old-age? How much HP am I down with 11 000 miles on the original top-end?
Thanks, for all your input. It would be nice to hear from an engine builder (Mr.Viper) concerning the questions above.
I keep my clutches in top condition (oil-lite brass bushings, new parts, everything very clean, and typically run a 8bu-10 set-up). I also have changed the gearing to 13 wide hyvo gears with a ratio of 23-39. My carbs are always spotless and I make sure my stock reeds are in top shape. I clean and adjust my powervalves at least once a season. I rebuilt my entire skid by fabricating brass bushings to significantly tighten everything up (way better weight transfer after fixing the skid).
The guys I ride with are constantly amazed at how fast my sled is. I would like to know if I am playing with fire since the top-end has never been touched. Is it just a matter of time till something goes? Would I notice a power increase if I did the top-end? The Yamaha parts would cost me about $600.00 and I would rather put the money towards another srx, but if I am playing with fire I will do the top-end. Do top-ends ever go due to old-age? How much HP am I down with 11 000 miles on the original top-end?
Thanks, for all your input. It would be nice to hear from an engine builder (Mr.Viper) concerning the questions above.
YAMMIEGOD3:16
Active member
KEEP A EYE ON YOUR COMPRESSION, USE GOOD OIL AND FUEL AND RUN IT. IF THIS SLED IS AS NICE AS YOU SAY, REBUILDING THE MOTOR SHOULD BE EASY. WHEN YOU ASK, '' DO THESE EVER GO '' SURE, WEAR AND TEAR, HIGH MILLAGE etc. PISTONS AND RINGS ARE EASY. 3:16 (yammie tony)
I know some guys have 17,000 miles on their motor without doing a top end. Like Tony says, find out your compression in each jug if you want a better picture of what your top end is doing right now.
The rings and piston skirts are wear items. How worn are yours? There is only one way to find out - take it apart, inspect and measure. A top-end rebuild should not cost you near that much even with genuine Yamaha parts. A compression check is a good thing to do, but does not tell the whole story.
Many run until they quit or the sled wears out. Personally I like to inspect every 5K or less.
If you go to that trouble with everything else, why not apply the same practice to the powerplant. If it does blow it will be over $600, or in your case likely a new sled.
Many run until they quit or the sled wears out. Personally I like to inspect every 5K or less.
If you go to that trouble with everything else, why not apply the same practice to the powerplant. If it does blow it will be over $600, or in your case likely a new sled.
rx1jim
New member
My 2000 SRX had 13,000 absolutely trouble-free miles on it prior to rebuilding the engine. Every year after 8000 miles I told myself I was going to rebuild the top end, just could not justify the rebuild since the engine still ran so very strong. I was forced to rebuild the entire engine after having a nuclear meltdown due to a tank of bad gas which ruined the center piston/cylinder is as little as a 20 mile ride. For the 2-3 seasons before the rebuild, the compression on all 3 cylinders was about 120 PSI and within 5% across cylinders. I did notice more discoloration on the piston below the rings which was a sure indication the rings were not sealing as well as they should be leading to "blow-by". A leak-down test would have probably told me the rings needed to be replaced. The engine will lose power gradually as the rings wear out, so gradual you will not feel it by "seat of the pants" measurements. I used Amsoil in the engine from the day I bought it. I inspected and measured EVERY part when I disassembled the engine. The cylinder bores (dia., taper and roundness) and piston diameters were well within the specs. Other than the discoloration on the pistons, they were fine. I could have simply cleaned them up by glass beading and reused them. Since I had to replace the center piston, I replaced all three pistons with new OEM pistons which I had Swain put a thermal barrier coating on the dome and a moly coating on the skirts. The crankshaft needed to have the connecting rod bearing replaced for the center cylinder due to the detonation meltdown but the crank was fine, no measureable wear, for cylinders 1 and 3.
I have been told by experienced engine bulders that high mileage two-stoke engines run the risk of piston failure in the skirt area if the piston to cylinder clearance gets too big and the pistons start rattling around in the bores. Clearly, had the detonation problem not occurred, i could have put a few thousand more miles on this engine prior to a rebuild. I credit the lack of wear on my pistons to 1. using a quality oil and 2. ALWAYS warming the sled up for at least 10 mins ( usually while I am putting my gear on, checking the fluid levels, checking the track, clearing ice out of the suspension) BEFORE putting a significant load on it. A warm up is important to prevent cold sscuffing of the hot pistons (expanded) on a cold cylinder.
In the future with my SRXs, i will make sure to use a dose of an octane booster to help prevent the same detonation problem. Having spotlessly clean carbs is critical with these engines as well as the right octane gas.
Jim
I have been told by experienced engine bulders that high mileage two-stoke engines run the risk of piston failure in the skirt area if the piston to cylinder clearance gets too big and the pistons start rattling around in the bores. Clearly, had the detonation problem not occurred, i could have put a few thousand more miles on this engine prior to a rebuild. I credit the lack of wear on my pistons to 1. using a quality oil and 2. ALWAYS warming the sled up for at least 10 mins ( usually while I am putting my gear on, checking the fluid levels, checking the track, clearing ice out of the suspension) BEFORE putting a significant load on it. A warm up is important to prevent cold sscuffing of the hot pistons (expanded) on a cold cylinder.
In the future with my SRXs, i will make sure to use a dose of an octane booster to help prevent the same detonation problem. Having spotlessly clean carbs is critical with these engines as well as the right octane gas.
Jim
I have never seen a engine go these 10,000-15,000 and such miles and not wear the skirts, I surely dont want to argue but its just what I see here on average. I am sure it depends on the use of the machine, quality of oil used and such. Usually after 5000 or so miles the rings do indeed wear and dont hold the piston as stabil in the bore and it rocks a bit, this is what wears the skirts, and over time it will eventually break off the skirt if allowed to wear long enough. The thing is these engine run like fine tuned watchs so its hard to take something apart when it runs so good everytime, but they do wear parts like any other 2 stroke does. If a 2 stroke could run for thousands of miles and need no engine matence we would have 2 stroke direct injected cars, because power to weight ratio they are king, but they do require piston/ring maintencae. the piston is the heart of the engine.
As mentioned, you dont notice the power loss because its so gradual and slow, but its there, theres lots of reading on this site on this stuff, search.
If you keep fresh rings in them they will keep the factory pistons in them for a LONG time. The good news is I have sent out pistons that are right on the edge of the wear spec up to swain tech. to have them coat the skirts in pc9 formula, they can build up to around .004" thick and this will get you back into the right clearance specs and get you plenty more miles from them, seems to work very well.
Theres many post here on this site about when to ring and rebuild, everyone has thier own opinion so.... you have to just simply check for yourself, take a micrometer and measure the skirts, then mic the cylinder, the differance is your clearance, check it against the specs from yamaha, thats all you can do!
As mentioned, you dont notice the power loss because its so gradual and slow, but its there, theres lots of reading on this site on this stuff, search.
If you keep fresh rings in them they will keep the factory pistons in them for a LONG time. The good news is I have sent out pistons that are right on the edge of the wear spec up to swain tech. to have them coat the skirts in pc9 formula, they can build up to around .004" thick and this will get you back into the right clearance specs and get you plenty more miles from them, seems to work very well.
Theres many post here on this site about when to ring and rebuild, everyone has thier own opinion so.... you have to just simply check for yourself, take a micrometer and measure the skirts, then mic the cylinder, the differance is your clearance, check it against the specs from yamaha, thats all you can do!