T500 wont run right

70Titan · Posted: Sat Mar 20, 2010 3:30 pm Post subject: T500 wont run right

Thought I would throw this out to you 2 stroke gurus. Ive got 2 1970 T500 Titans that I just got running. Both are in approximately the same condition on the top end. Just a light hone job and new rings, new gaskets, carb cleaning. Both bikes were assembled at the same time. One runs very well and goes down the road nicely. The other does not have any power. I have to slip the clutch to get it rolling and it wont rev very high. I at first had a problem with the petcock but I replaced the vaccuum hose and it then started right up. I have not swapped the petcocks yet. I opened the gascap to rule out the vent hole. Whats the symptoms of bad crank seals? I didnt replace either of the bikes crank seals. Is it possible to do for a shade tree mechanic or does someone have to rebuild them for me? Thanks for your time. Scott

Russell · Posted: Sat Mar 20, 2010 4:22 pm Post subject:

Before you think the worst(crank seals) if the baffles are still in your mufflers how gunged up (or not ) are they?Clean baffles and cleaned out mufflers can make a BIG difference to the way a T500 runs.
Its also not hard to disturb the points while working on a T500 if the motor is out of the bike.I'm such a ham-fist that presumably while lifting the motor around I managed to damage one set of points such that the faces of the points were mis-aligned. Wouldn't idle cleanly and wouldn't rev out but would stumble along on low throttle openings. Took me a long time to track that issue.

dorT500 · Posted: Sat Mar 20, 2010 6:16 pm Post subject:

The bike may run just alright with a bad crankseal/crankseals (two center and two outboard seals) Plugs may be black and oily and might smoke more out of one side than the other if just one is bad. Normally you would notice it is sipping/burning tranny oil when upon checking oil level at various times but you probably have not ridden it enough to notice a change in level the way it is running right now. I would probably swap out the battery from the bike that is running well and also go over electrical and carb troubleshooting again. Do you have a manual. Maybe check the carbs again and add inline filters. Air filter foam (oiled) intact and not 'flaking' apart? Hopefully the seals are not bad but always a possibility after sitting a long time. As you may already know, the replacement of the center seals and center 'O' rings require the crank to be split. A job best left to a professional. Labor only from Bill Bune enterprises is around $125.00. There are other sources. Here is a link to pressure testing. There are other ways to do it. I am not sure if Stu (Bikegeezer) has his own procedure already documented somewhere. Other info can be found just by typing in keywords ' pressure testing two strokes. If it comes down to it as mentioned in this link the right outboard crank seal can be replaced just by removing the clutchcover. Of course, as mentioned earlier...go for the simple solutions (electrical/fuel) first with a step by step troubleshooting procedure that would be in a manual. Good Luck

http://www.motorcycleracer.net/phpBB2/viewtopic.php?t=1618&highlight=pressure+testing

Edit: (note on air filter...yours would be a paper filter I believe on the '70 model)

Bikegeezer · Posted: Sun Mar 21, 2010 6:31 am Post subject:

I agree - check carburetion and ignition items first. Also clean the baffles. Set the petcock to "prime" and confirm good fuel flow. Test it again in the "on" position using a vacuum pump on the vacuum line. If the petcock leaks vacuum, you'll have a fuel starvation issue as well as a vacuum leak at the left cylinder.

If you need to pressure check your Titan, here's a procedure you might find useful.
Install the spark plug to normal torque. Seal the exhaust with a double layer of inner tube material. Grease both sides at the outer diameter to seal it good. You can see by the rubber sucked inward that this cylinder has vacuum in it.

Get an appropriate sized rubber cork and brass nipple from the hardware store. Attach a combination vacuum/pressure gauge and a MityVac hand pump. Rule of thumb - The cylinder should hold 6" of vacuum and 6psi pressure with no bleed down for at least 6 minutes.

If it leaks, don't automatically assume bad crank seals. Pressurize it, and spray soapy water around all of your test fittings, the base gasket, head gasket, spark plug, oil line fittings, manifold/cylinder head joint. If no leaks at those points, check the left crank seal with soapy water. Remove the oil filler plug, and listen for hissing noise. Then move your test gear to the right cylinder, and repeat.

Stu

dorT500 · Posted: Sun Mar 21, 2010 11:14 am Post subject:

Thank you Stu for posting those pics and info. Back somewhere in the VJMOG I had posted how I had made something similar to the testing pieces/block off plates in the link below. Mine were thin raw stainless plates with rubber gasket membrane. I had taken a copied picture of the rig they showed below to a couple of hardware stores. One salesclerk said the big brass fitting part looked like something that may have been used on old water well equipment. Idunno

Anyway, I just wound up using the pvc plus a combo of brass fittings to accommodate the gauge (that I never got around to getting, I wanted a high quality low pressure only gauge) and a schrader valve. This was before I had seen setups similar to yours.. ...man I really need to break down a get a new digital camera to keep myself from being so long winded. Anybody have an extra used high quality working digital camera they want to trade for some T500 parts? Wink

http://atv.off-road.com/atv/article/articleDetail.jsp?id=190479

' 70Titan' Have you changed the spark plugs? Even if new? Maybe it is only running fully on one cylinder. Felt the exhaust coming out of both mufflers to see if it seems equal? I recall one time when on the freeway I started losing power. I thought for a second I was running out of gas...but knew better. I pulled off the freeway and felt the muffler exhaust( one side was obviously weaker) and changed that side's spark plug. If I remember correctly, it was not fouled but I went ahead and installed another plug in it and away I went. It was like it just quit working. Either that or a temporary clog in that cylinder's carb. I really think it was just that plug that was bad...and it had been barely used.

70Titan · Posted: Mon Mar 22, 2010 7:22 pm Post subject:

Ok, thanks for all the quick responses. Ive got a day off Wednesday and a good running bike to swap out some parts so I'll let you know what I find out. I do have brand new plugs in the poor running bike but have not swapped them out yet. I have some leak-down paraphenalia that I used for an RD400 so maybe I can get that to work if the other easier things dont work. I'll get back to ya, thanks!

Steve Searles · Posted: Tue Mar 23, 2010 10:27 am Post subject:

Very good info here guys. Well done. Usually the symptoms of a bad crank seal are: it sucks too much air which makes it run lean which makes the engine rev high uncontrollably at times. Or when you rev it up the revs don't come back down quickly due to lean condition. Erratic running is there, hard to start with loss of power but the high revs gives it away most of the time.

Bikegeezer · Posted: Wed Mar 24, 2010 3:40 pm Post subject:

Russell · Posted: Wed Mar 24, 2010 3:47 pm Post subject:

Stu.Its past well past March 22nd here.Does that mean you've had that chassis rebuild?

Whoops...you posted an answer while I was typing.

BenEberle · Posted: Mon Aug 02, 2010 10:26 pm Post subject:

I'm going to jump in this one too, since my '74 T500 is having some odd behavior. It runs, and runs pretty darn well. I do think that the charging system has issues since it's killing my new battery like it's nobody's business. But that's a different story. When the battery is fully charged, it starts on the first kick, and after a short warm up idle session, runs like a bastard. The issue I'm seeing, however, is that the left exhaust is smoking like a tire fire where the right exhaust is clean, clean, clean. I road tested it today and it will ride up and down the power band to the redline and back down just fine. However, it does have a high idle after a hot run - like, around 3k RPM. It'll settle down after a little while, but it does seem like it's lean somewhere.

My big question is what you all think about the difference in pipe smoke. That kind of concerns me. I have another issue with the carbs, mainly that the float valves don't work right and they leak gas like a mother after sitting for a bit. But I don't think that is contributing to the smoking.

Anyways...this thing is loads of fun and is close to running perfectly, I believe. What do you think?

Thanks in advance for the help.

jws3 · Posted: Mon Aug 30, 2010 6:32 pm Post subject: What color is the smoke?

If white I'd suspect a bad crank seal. Have you checked the level of transmission fluid? Burning fluid can make white smoke and a lot of it! Had this issue on my old '79 TS185.

CaptCatFish · Posted: Tue Aug 31, 2010 1:28 am Post subject:

I suspect bad crank seals as well. I'm struggling with similar issues on a 1972 T500.

Does it have crankcase drain plugs? My T500 has one for each cylinder (see DorT500's posts about this). I'm getting oil drainage from my smoking right side cylinder even after completely draining it and then running it for just 3-4 minutes. I collected the oil in a clear cup and its definitely tranny oil.

I may have overfilled it so gonna change it again and keep my fingers crossed. However, I suspect my center crank seals will have to be replaced (the outer ones already have been replaced).

The good news is that if the crank has to be done, getting to it is pretty straightforward. I was able to split the cases on my donor motor yesterday in about two hours. The hardest part may be getting out the credit card AGAIN.

CaptCatFish

BenEberle · Posted: Thu Sep 02, 2010 7:59 pm Post subject:

You know, I started to think about that. It's white smoke, but not billowing. In fact, after a while, it clears up pretty good. I think there very well might be a slight leak, but also I believe my carburetion isn't right yet.

Thanks for the ideas. I think you're right on there. I'm going to ride it as is for the fall....keeping it topped off, and then give it to my 2-stroke mechanic to split and rebuild. I simply don't have the tools or total know-how to get that job done.

CaptCatFish · Posted: Fri Sep 03, 2010 2:13 am Post subject:

Did you remove the crankcase drainage bolt on that side? (see DorT500's pics in another post). I'm curious to know if anything comes out of the crankcase drainage bolt on the smokey side. If anything is there, catch it in a clear container so that you can smell it and look at the color.

My T500's excessive smoking on one side problem seems definitely related to the consumption of tranny oil, especially since there is at least an ounce of oil that drains from that side after every run. If yours is more related to excessive carb/fuel/float level, seems to me that the drainage from that side (if any) would smell of gasoline and have significant diluted injector oil.

CaptCatFish

BenEberle · Posted: Fri Sep 03, 2010 12:00 pm Post subject:

Yeah, Capt. There's an excellent chance that my issue with the float on the left carb getting stuck (it leaks periodically out that carb for no apparent reason other than 1. the float is probably bad and there might be some shit stuck up in the float valve or....2. the petcock doesn't seal well.). Maybe I'm just grasping at straws in hoping that the seals are still good....but there is a chance that that leaky float is spilling gas into the cylinder.

I have yet to pull that plug and look. All my tools have been in another garage for an old moped project. I'm picking them up this weekend to go see what's up with the left cylinder.

Thanks again for all the good advice. This bike is so much freakin' fun, I'm so glad I get to ride it for the fall.

PS: Another pick of it with the lower bars. Really like how it handles.