Hey guys a good friend of mine is beyond upset at this point the bike sounded like it was only running on 2 with no power, we went through the fuel, ignition/timing etc. and nothing, we did a compression check on cylinders 2-3 and they were way below with no compression, 1-4 were good @ a 1.25 i believe. White smoke pouring out the exhaust, oil all over on the muffler tip.. the bike has 25,000 miles roughly which is why i find it hard to believe the motors already toasted! you think its because he just ran it too hard all the time? is there any possbility that hte motor isnt toasted?
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John 3:16 -
1.25 what?
What do the plugs look like?
Did this happen all of a sudden or over time? -
Make sure the throttle is all the way open when checking and I would also check the valve clearances. So unless he ran it without oil Worst case it may need a new set of rings, or he may have burn't a piston if it wasn't properly jettedComment
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check and check, there was oil in the bike as well. are the rings a hard job? we can do valve adjustments no problem i dont thing a ring repair
i dont know i just heard the guy (bike shop owner whos a good friend) say a buck and a quarter. the plugs
!! two of em were destroyed as in the tip/electrode whatever you wanna call it was GONE-non existant blown to smitherines. and the other two were snow white. we threw in new plugs hoping it would pass but still is no good! I believe it happened all of the sudden. We really thought it was ignition timing because it happened out of no where, its not, swapped all the parts on my 750 and it worked fine.
John 3:16Comment
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A compression test is completely meaningless without ensuring the valve clearances are correct first. Too tight and compression will read zero, even on a perfectly good engine. Hopefully he didn't run it hard with them way too tight until the valves burned up.Comment
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Snow white plugs sound lean, piston maybe?check and check, there was oil in the bike as well. are the rings a hard job? we can do valve adjustments no problem i dont thing a ring repair
i dont know i just heard the guy (bike shop owner whos a good friend) say a buck and a quarter. the plugs!! two of em were destroyed as in the tip/electrode whatever you wanna call it was GONE-non existant blown to smitherines. and the other two were snow white. we threw in new plugs hoping it would pass but still is no good! I believe it happened all of the sudden. We really thought it was ignition timing because it happened out of no where, its not, swapped all the parts on my 750 and it worked fine.Comment
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snow white is EXTREMELY lean. there is surely internal damage of some sort.Comment
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makes me not want to beat on my bike now!John 3:16Comment
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does anyone know of a compression chart that can fortell the future if your motors soon to be blown out?John 3:16Comment
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Beat on it all you want once the maintenance is done and it's running correctly. These engines are bullet proof, however they are not idiot proof.
No chart, just adjust the valves and check the compression again, then ride it several hundred miles and do it again. The compression will come back up, unless the valves have been too badly burnt.
I have seen three neglected GS engines this summer, with zero or near zero valve clearance, and as a result, no compression on one or more cylinders. There can be no compression if the valves are not closing. If this is the case, the valves will start to burn, but if it's caught early enough, it may not be too serious.
After a valve adjustment these engines had some compression. After riding a thousand miles or so the compression got better and better. Will it ever get as good as the other cylinders? Maybe, maybe not, it depends on how much the valves were damaged. Two of these engines are still out riding around, several thousand miles on each. The other hasn't really been on the road yet for other reasons, but it's running fine, starts right up, idles smoothly, doesn't smoke.
In the future, it's a good idea to do these simple checks before ruining the engine. Much simpler to repair before there is too much damage.Comment
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Usually when you have plug like described and no compression means overheating and gulling on the pistons or maybe even holes in them. An old mechanic trick is to squirt some oil in sparkplug hole and recheck compression. If compression goes up then the rings are bad, if not it is valves, head gasket or a hole in piston. A leak down tester could help find the problem too. I can?t say what could have overheated the pistons but it is usually too lean, too hot plug or oil problem.
Could have bent a valve but that shouldn?t have caused the plug damage.
You will probably have to pull the head to be sure and do a top end.Comment
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Quit guessing. adjust the valves and go from there.
bent valves? I've had my '82 up around 11K rpms MANY times and have never bent one yet.Comment
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Ditto
I can go past 10K RPM, no problem in the lower gears
If it got hot enough to melt a piston, the exhaust should be gold, if not blue
Without knowing how this bike was maintained, we're kinda shooting in the dark here
Bad coil? switch the coil wire and see if it fires on the other cylinders
Wait - what year GS 1000? Does it have points?1978 GS 1000 (since new)
1979 GS 1000 (The Fridge, superbike replica project)
1978 GS 1000 (parts)
1981 GS 850 (anyone want a project?)
1981 GPZ 550 (backroad screamer)
1970 450 Mk IIID (THUMP!)
2007 DRz 400S
1999 ATK 490ES
1994 DR 350SESComment
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