97 Yamaha RT100 Bogging Issue

[illSHOyou]

Hello,

I recently purchased a 97 Yamaha RT100 and I am having issues with it bogging over time and stopping. When we first got the bike it would run fine for about one blast down the street and as you slow down you could hear the engine start to bog and die. When the engine started to die you would have to give it almost full throttle to keep it running, and even at full throttle the bike will continue to run but the engine doesn't really accelerate. We then started with cleaning the carb and checked for factory settings. All jets removed cleaned, float bowl height measured, needle clip checked, pilot screw 1 1/2 out from seated position. The bike still has the same reaction. I really don't know what to blame. We did fuel throttle passes and pulled the plug, and the plug is really wet, but I don't know if its too much fuel or oil. Even though we cleaned the carb i wonder if the float is to blame? I was hoping that somebody could shed some light on this problem, I have 6 hours of work into the bike and I am running out of ideas.

Hopefully one of you 2 cycle guru's could tell me exactly whats going on.

One more note, the bike smokes blue alot on startup and after running for a short period fuel/oil is just dripping out of the exhaust. I think its running too fat, but maybe things happen to the oil pump I just dont know....

[illSHOyou]

Hello,

I recently purchased a 97 Yamaha RT100 and I am having issues with it bogging over time and stopping. When we first got the bike it would run fine for about one blast down the street and as you slow down you could hear the engine start to bog and die. When the engine started to die you would have to give it almost full throttle to keep it running, and even at full throttle the bike will continue to run but the engine doesn't really accelerate. We then started with cleaning the carb and checked for factory settings. All jets removed cleaned, float bowl height measured, needle clip checked, pilot screw 1 1/2 out from seated position. The bike still has the same reaction. I really don't know what to blame. We did fuel throttle passes and pulled the plug, and the plug is really wet, but I don't know if its too much fuel or oil. Even though we cleaned the carb i wonder if the float is to blame? I was hoping that somebody could shed some light on this problem, I have 6 hours of work into the bike and I am running out of ideas.

Hopefully one of you 2 cycle guru's could tell me exactly whats going on.

One more note, the bike smokes blue alot on startup and after running for a short period fuel/oil is just dripping out of the exhaust. I think its running too fat, but maybe things happen to the oil pump I just dont know....

Bump for help... Anybody? Or does this little bike have everybody stomped?

[Airhead]

and the plug is really wet, but I don't know if its too much fuel or oil. Even though we cleaned the carb i wonder if the float is to blame? I was hoping that somebody could shed some light on this problem, I have 6 hours of work into the bike and I am running out of ideas.

Hopefully one of you 2 cycle guru's could tell me exactly whats going on.

One more note, the bike smokes blue alot on startup and after running for a short period fuel/oil is just dripping out of the exhaust. I think its running too fat, but maybe things happen to the oil pump I just dont know....

Sounds like crank seals to me, does the transmission oil smell of fuel?

[illSHOyou]

Sounds like crank seals to me, does the transmission oil smell of fuel?

That seems to make alot of sense. Perhaps the engine starts to injest too much oil because the seal is leaking making combustion unstable and make the engine want to die. If you hit the fuel inrichment circut combustion becomes stable again because the added fuel makes up difference for the added oil in the engine. Also, what would happen if someone where to run ATF in the transmission instead of 30 weight motor oil? Would it ruin the seals?

[Airhead]

That seems to make alot of sense. Perhaps the engine starts to injest too much oil because the seal is leaking making combustion unstable and make the engine want to die. If you hit the fuel inrichment circut combustion becomes stable again because the added fuel makes up difference for the added oil in the engine. Also, what would happen if someone where to run ATF in the transmission instead of 30 weight motor oil? Would it ruin the seals?

Cant see ATF fluid being an issue on the seals although I wouldnt recommend it as a lube. The seals may be just worn out, the seal on the left will suck air in and the one on the right (clutch side) will suck oil in and cause smoke. To some extent fuel will pass into the oil and can sometimes be detected by the smell. Trouble is its an old bike and you dont know its history, like when they were changed last

[illSHOyou]

Cant see ATF fluid being an issue on the seals although I wouldnt recommend it as a lube. The seals may be just worn out, the seal on the left will suck air in and the one on the right (clutch side) will suck oil in and cause smoke. To some extent fuel will pass into the oil and can sometimes be detected by the smell. Trouble is its an old bike and you dont know its history, like when they were changed last

I change transmission oil the other day and found ATF to be in the trans. I then added 30 weight oil. Today I pulled the plug and it smelled of gas pretty bad and was dark in color, much like the oil that is injected into the bike. So I am pretty sure it needs new crank seal, and I think that pretty much sums up why it burns so much oil through the exhaust.

[illSHOyou]

I still can not figure out the problem with this bike. I feel like ripping my hair out!

We bought 2 new crank seals. I replaced the seal on the transmission side becuase we suspected the engine sucking oil from the transmission case, and due to a gas smell in the new transmission oil. I was unable to replace the other seal due to not having the puller tool. Still after replacing the one seal the bike is still not running right.

I have taken a can of carb cleaner around the whole engine and found no air leaks, no change in rpm nothing.

1. The bike fires up just fine

2. Idles about 1 min. during the heatup cycle before issues start to show

3. Engine rpm begins to drop and you open WOT to catch it, its starts to catch but is very hit and miss and sounds like the spark is being blown out, while the exhaust starts to get very smoky.

4. Open up the fuel enrichment circuit, crack wot a few times and everything is great for approximatly 1 min. then the cycle repeats untill the enrichment circuit is opened again.

It appears to point to a rich condition becuase of the bogging, but if that were true, when you activate the choke things should get worse not better. There is still the posibility of the opposite side crank seal leaking air, which I guess would point to why the choke stabilizes the engine.

The carb has been rebuilt to factory specs 4 times and cleaned. This bike is a trail bike, it has no mods. Stock settings should be right on the money, but it doesn't work.

There is something about why the bike stabilizes when you hit the choke fuel enrichment, but I don't know what its correcting when I blip the choke? Its really the only indicator that could point to the problem, but I don't know what it means other than the bike is getting more fuel, but why does simple opening the choke correct the bike for a short period of time?

I think the bike will run at WOT, but only if you could run continues at WOT.

Oil pumps are supposed to be trouble free and low failures, buts its not really adjustable anyway?

Its my lack of 2 cycle experience to identifie this problem and its driven me nuts.

So recap:

No outside air leaks

Carb Rebuilt

Transmission crank seal replaced

Other crank seal not replaced yet...

One more note:

When fuel switch is on fuel does leak out of the air cleaner when the bike is in the upright position. Is that normal? Float height measured out correctly to specs, and needle seat looks fine. Still doesn't explain why the choke circuit stabilizes the bike, becuase this would be another rich problem and the choke should not work if the carb is flooding the engine...?

[Airhead]

You definitely have a problem with fuel level if it is comin out of the carb whatever you say about the valve condition...try tapping the carb with a hammer shaft in case the float has somehow stuck.

Also it is behaving like a blocked pilot jet scenario?

you say it starts fine..ON CHOKE?

idles for 1 min....ON CHOKE?

it is hardly going to be warmed up after just 1 minute is it?

[illSHOyou]

You definitely have a problem with fuel level if it is comin out of the carb whatever you say about the valve condition...try tapping the carb with a hammer shaft in case the float has somehow stuck.

Also it is behaving like a blocked pilot jet scenario?

you say it starts fine..ON CHOKE?

idles for 1 min....ON CHOKE?

it is hardly going to be warmed up after just 1 minute is it?

I suspect a potential issues with the float. So I tried turning the fuel shut-off On/Off to control fuel into the carb. Still has the bogging issues after idling for a bit.

The bike starts on choke immediately, and then I switch it off. Immediately after shutting the choke off, I can blast down the street 1/4 mile and it runs fine. Which tells me the jetting is working or at least not clogged. But once you start to take a easy around and not use WOT, the bike will eventually die unless you hit the choke, then everything is fine for another blast down the street.

This is by far the most F'ed up thing I have every seen.

If rings where a issue than the bike would be hard to start. I plan on getting a compression check soon just for grins.

IF the carb was messed up and flooding the engine then why does activating the choke (which adds more fuel) correct the problem temporarily?

Also, If the engine had a air leak wouldn't it at least run and at least try to fry a piston?

[Airhead]

Well if the choke is off and you are not WOT then you have problems

The pilot jet should feature under these conditions. Have you seen daylight through this thing?

[illSHOyou]

Well if the choke is off and you are not WOT then you have problems

The pilot jet should feature under these conditions. Have you seen daylight through this thing?

Yes, All jets cleaned and fine wire ran through ports, Air pressure applied to carb passages. Held up to light to see if clogged.

This bike fires up and runs great for X amount of time and then tries to bog out. Hit the choke and everything is fine for x amount of time again.

You have the choice before X amount of time hits to let the bike idle or do a blast down the street. Less time after a blast down the street and more time with it just setting and idling. I really thought the oil pump was to blame, but after reading up on it doesn't seem to be the case. I don't really have any key symptoms that point to the problem.

The searches I Have done:

Crank seal symptoms

WOT then Dies

Bad oil Pump

Carb adjustments

YOU Tube Videos

Rich Conditions

Lean Conditions

2 Cycle symptoms

etc....

[illSHOyou]

Yes, All jets cleaned and fine wire ran through ports, Air pressure applied to carb passages. Held up to light to see if clogged.

This bike fires up and runs great for X amount of time and then tries to bog out. Hit the choke and everything is fine for x amount of time again.

You have the choice before X amount of time hits to let the bike idle or do a blast down the street. Less time after a blast down the street and more time with it just setting and idling. I really thought the oil pump was to blame, but after reading up on it doesn't seem to be the case. I don't really have any key symptoms that point to the problem.

The searches I Have done:

Crank seal symptoms

WOT then Dies

Bad oil Pump

Carb adjustments

YOU Tube Videos

Rich Conditions

Lean Conditions

2 Cycle symptoms

etc....

Bump for Help...

Please I really need help on this bike, or redirected to another forum that might most likely know my problem.

Thanks

Sean

[Airhead]

Its an odd one. Do you think the exhaust may be blocked up?

I have heard of but not put into practice the 'vacuum cleaner test' whereby you connect a cylinder type vacuum cleaner to the exhaust (cylinder end) and if the vacuum cleaner races like it would with your hand over the end it is an indication of a blocked exhaust.

Having said this though do as necessary with and baffles etc that are removable.

[illSHOyou]

Out of curiosity could I have a air leak between the case halfs?

How would they seal the two halfs together? I am not seeing a gasket. Perhaps RTV? Would a air leak between the case halfs let fuel and oil make it into the transmission case, even though the right PTO seal is brand new?

I need to drain the transmission oil again and see if I smell fuel again after the PTO Crank Seal replacment.

[Airhead]

The seal is by liquid gasket.

By the way you can test by putting a pipe on the transmission case breather spigot into something like white spirit in a jar. watch for bubbles when the engine is run and revved. This will indicate a fault with the right crank seal or indeed crankcase half sealing.