Hope someone out there can help. I have a low mileage (8000 kms) 1973 Suzuki GT250 K. The weather yesterday was good in the Adelaide Hills so went for a ride, the bike had been sitting for about 3 months. After about 20 minutes of riding suddenly lost power just as if I had run out of fuel and rolled to a stop, checked that I had fuel and restarted but the bike was running rough. As soon as I put any load on the engine by letting out the clutch the motor would load up and die before the bike would move off. Managed to get home by pushing the bike and then once I got rolling down a hill was able to bump start and limp home in first gear, tried second gear but as soon as revs dropped below 5000 it would threaten to stall. Once home I pulled the plugs L/H seemed OK but R/H was dry with a dark but not sooty or wet coating. Both had spark and changing plugs made no difference. From checking exhaust while running feels like the R/H cylinder is not firing. Removed the air filter box, L/H carb has vacuum and the R/H also but markedly less. Looked as if the R/H carb had spat some oil into the air filter boot but only a small amount and it seemed more like 2 stroke oil than trans oil. Disassembled the R/H carb hoping to find it full of crud but seemed pretty clean and had fuel in the float bowl. Having reached this stage I'm starting to think (centre?) crankshaft seals, bike doesn't smoke excessively however, in fact runs really clean for a 2 stroke. Also doesn't seem to be using any trans oil. Can anyone advise how to confirm or eliminate the crank seals before I spend time on cleaning and rebuilding the carbs. Being the eternal pessimist if it is the centre crank seal does anyone know if there is someone in the Adelaide area who could do the crank repair as I understand it has to be pressed apart and back together.
Hey GT250KDave Welcome to the forum, sorry it's not under better circumstances. I have read several times your posting and still have doubts about your problem (in my mind). By your reckoning seems not to be firing on the r/h side, and you claim you are getting spark and the r/h plug is not wet, kinda makes me think that you have a carb issue on the r/h side. My simple deduction is this: If fuel was getting in on the r/h side with adequate spark, she would fire. With the plug dry it would appear no fuel is getting in, so I guess a quick check of the carb r/h side would be my first move. Keep us posted mate, it's a 2 stroke, can't be too hard.
Hi Phil, thanks for the welcome. Hadn't thought of it that way but you are right, I will persevere and clean/rebuild the carbs, have to order some parts but will keep you posted.
Hi Dave, welcome to the forum. I would also check you condenser and points as this will also seem to be a fuel problem but is actually a weak spark not bridging the plug under compression. Maybe check your coils with multimeter if available. Try a compression tester to see if you crank seals are leaking.
Thanks Murdo, will be getting a compression tester tomorrow, can you tell me what sort of results I will get if the seals are shot? Did have a good healthy spark but will check coils etc.
In case u havnt already found it the parts cat for the GT250K is here..... http://2fiftycc.com/index.php?resources/suzuki-gt250-k-l-m-a-b-c-parts-catalogue.141/ and manual ... http://2fiftycc.com/index.php?resources/suzuki-250-350-twins-owners-workshop-manual-part-1.165/ http://2fiftycc.com/index.php?resources/suzuki-250-350-twins-owners-workshop-manual-part-2.166/
check the battery voltage as i had similar problem with a yammy twin and 1 cylinder would drop out and was a flat[dead] battery.
The manual above should tell you, but roughly anything below 40psi and you will need to break out the spanners. Remember to hold throttle wide open when checking compression.
Ignition system and battery all tested fine. Had a play with the front caliper as during my push home found that the front brake was binding slightly. Just a tip if you do the same for what it cost me for 4 orings and 4 dust caps you can get a complete rebuild kit (including caliper piston and seals) on ebay for less. That will teach me not to ask how much when I order by phone!! Anyway back to the problem at hand, got the compression tester and the good news is that the centre crankshaft oil seal seems OK, the reason I am pretty sure of this is that I first tested the L/H cylinder (carbs have been removed) which came in at 120 psi, which I was pretty happy about, R/H side came in at a big fat zero didn't move the gauge at all. I'm guessing a hole in the piston crown which now I think about it would explain the dark grey coating on the spark plug, (molten aluminium) Spanners will come out tmrw if I get a chance and just hope no other damage has been done. A few Jack and cokes tonight I think to wash away the pain. Thanks to all for the help so far.
Sorry to hear the news Dave, you'll soon see as soon as the heads come off. Keep us posted mate and good luck.
