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Sorry to post yet ANOTHER rejetting question... but this one has me stumped.
1980, GS850 (32,000km) completely stock.
I noticed a lack of power on the highways from 1/2-full throttle so I figured plug chops could shed some light on the subject.
2/3 Throttle in 3rd gear @ 80-90km/h on a fairly steep hill
Full throttle in 5th @ 100-120km/h on a moderate incline
I was able to hold the throttle for about 2 mins each time and killed the bike without closing the throttle, pulled over and checked the plugs.
Both chops ALL of the plugs look like #22 or #23 in the above link (they reminded me of brand new plugs, smooth/shiny white insulators).
There is a fairly new air cleaner on the bike, the airbox doesn't have any mods to it (although I think one of the seals could be better). The last compression test indicated low compression on the #3 cylinder, valves were OK (probably could use adjusting now). I have rebuilt the carbs (cleaned and replaced with identical parts), adjusted the airscrews, adjusted the float heights (verified with a fuel guage) and synced the carbs (set for 2&3 lower vacume than 1&4). New intake O-Rings and boots, new airbox boots, petcock seems to be working and flowing fuel to the carbs. Dyna coils on order to replace a possible intermittant coil problem.
At first I thought there might be a fuel blockage in the line, but unless the problem is a blockage at the petcock, fuel line or "T" I shouldn't be getting the same problem on all 4 cylinders. Same if somehow the problem is caused by valve clearence or compression problems, I should see 1 or 2 bad cylinders and the others OK. I am thinking about rejetting but as per the advice from this forum, stock bikes generally don't need to be rejetted...
1980, GS850 (32,000km) completely stock.
I noticed a lack of power on the highways from 1/2-full throttle so I figured plug chops could shed some light on the subject.
2/3 Throttle in 3rd gear @ 80-90km/h on a fairly steep hill
Full throttle in 5th @ 100-120km/h on a moderate incline
I was able to hold the throttle for about 2 mins each time and killed the bike without closing the throttle, pulled over and checked the plugs.
Both chops ALL of the plugs look like #22 or #23 in the above link (they reminded me of brand new plugs, smooth/shiny white insulators).
There is a fairly new air cleaner on the bike, the airbox doesn't have any mods to it (although I think one of the seals could be better). The last compression test indicated low compression on the #3 cylinder, valves were OK (probably could use adjusting now). I have rebuilt the carbs (cleaned and replaced with identical parts), adjusted the airscrews, adjusted the float heights (verified with a fuel guage) and synced the carbs (set for 2&3 lower vacume than 1&4). New intake O-Rings and boots, new airbox boots, petcock seems to be working and flowing fuel to the carbs. Dyna coils on order to replace a possible intermittant coil problem.
At first I thought there might be a fuel blockage in the line, but unless the problem is a blockage at the petcock, fuel line or "T" I shouldn't be getting the same problem on all 4 cylinders. Same if somehow the problem is caused by valve clearence or compression problems, I should see 1 or 2 bad cylinders and the others OK. I am thinking about rejetting but as per the advice from this forum, stock bikes generally don't need to be rejetted...
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