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This is a Stage 4 200 on a mid ‘70s Jet 200. It has only done around 1000 miles once I built it.

Whilst going for a short ride a couple of weeks ago, the scooter seemed to be suffering fuel starvation. I filled up and then kept going. I was trying to identify whether the poor running was happening at a specific throttle opening. It seemed to be happening when the scooter was under load rather than a specific throttle setting.

When I got some more petrol, violent backfires followed by plumes of white smoke.

Blocking the tailpipe didn’t stop the engine so I think I can safely assume that I have blown the drive side oil seal.

Since then, I have taken off the flywheel, stator, exhaust and side casing so I could do a leak down test and, as I assumed there would be a leak, trace where it was coming from.

Essentially, the engine is largely airtight. It held pressure for a few hours although, overnight, it did lose pressure.

My question is, before I drop the engine and go any further, would a blown drive side oil seal still hold pressure? I can see the logic that it may be if the top end and mag housing seal is airtight.

PS, I have checked that I put petrol in rather than diesel and I have checked that the exhaust isn’t blocked.

I always had simlar symptons, after chatting to Ben at AF he pointed me towards the 8000 Motul oil i was using it turns out some of the race pre mix oils are very heavy and unless thoroughly mixed in a jar like at the racing, then they are likely to sink straight to the outlet in your fuel tap hence not mixing with the petrol until it has swished about the tank for a good while........
so i always had plooms of white smoke and lean running after filling with fuel, so the carb was getting a helping of 2 stroke and little petrol, solution was to make sure and always run injector oils instead of pre-mix!!!!
To note pre-mix has about 10% more lube than injector but only when properly mixed which aint possible in a tank.....not saying this is the case with all pre-mix oils but it was a problem with the motul 8000.

Maybe nowt to do with your issue but something to note.

shamrockexpress wrote:I always had simlar symptons, after chatting to Ben at AF he pointed me towards the 8000 Motul oil i was using it turns out some of the race pre mix oils are very heavy and unless thoroughly mixed in a jar like at the racing, then they are likely to sink straight to the outlet in your fuel tap hence not mixing with the petrol until it has swished about the tank for a good while........
so i always had plooms of white smoke and lean running after filling with fuel, so the carb was getting a helping of 2 stroke and little petrol, solution was to make sure and always run injector oils instead of pre-mix!!!!
To note pre-mix has about 10% more lube than injector but only when properly mixed which aint possible in a tank.....not saying this is the case with all pre-mix oils but it was a problem with the motul 8000.

Maybe nowt to do with your issue but something to note.

That is really interesting. I am not using Motul 8000 but I did think that the petrol colour in my petrol pipe was rather red tinged (the oil is red). I have been using this oil but not for very long



Thanks for the reply.

I may still have a drive side oil seal that is blown mind. The engine definitely kept running, albeit badly, when I blocked the tailpipe.

I have just checked the spec for the Smith and Allan oil. It says injector and premix.

Potentially going in the wrong direction for your problem but on the topic of oils, years ago I got a deal on a load of bottles of competition grade Rockoil premix, which worked perfectly when I bought it. However, as soon as the season changed and we had a couple of cold mornings, I ran into problems! Basically, every time we had a cold night the oil would separate and fall out of suspension, leaving a thick sludge in the bottom of tank and float bowl, requiring a strip down each time. Whilst the oil may have been ideal for warm weather competition, with fuel being mixed / vigorously shaken before a race, it was completely useless for general use.

I'll revisit the initial issue now...

My thoughts on initial query...

DO NOT ASSUME THAT THE FUEL YOU BOUGHT IS NOT THE PROBLEM!!!

As you immediately ran into problems post-fill up, with plumes of white smoke, this is exactly what I and others have experienced a number of times after filling up with contaminated fuel, typically contaminated from the pump (big name stations too!) and assumed to be diesel contamination.

An easy check is to empty the float bowl and fill from a different/new source. FYI - When I did this for a friend, it took a couple of kicks to start, then billowed white smoke (unburnt fuel in exhaust) then ran clean but started to die as float bowl emptied. We then flicked back on the fuel tap and the engine went from running well to lumpy and died quickly after. Draining the tank and refilling cured it, after we had stripped the float bowl again

A new issue so quickly after a refill... don't assume all is well.

Adam_Winstone wrote:Potentially going in the wrong direction for your problem but on the topic of oils, years ago I got a deal on a load of bottles of competition grade Rockoil premix, which worked perfectly when I bought it. However, as soon as the season changed and we had a couple of cold mornings, I ran into problems! Basically, every time we had a cold night the oil would separate and fall out of suspension, leaving a thick sludge in the bottom of tank and float bowl, requiring a strip down each time. Whilst the oil may have been ideal for warm weather competition, with fuel being mixed / vigorously shaken before a race, it was completely useless for general use.

I'll revisit the initial issue now...

I am fairly convinced that my oil is an issue and that this has kicked in as the weather has got colder. If I think back to me running around to jet the PHBL25 in, I do believe that I did have issues with lean running in the first couple of miles when the engine was under load going up a hill. This would clear after a while. With hindsight, I did see pockets of red oil forming in the petrol pipe too.

Initially, I put the poor running down to the cast iron barrel still being cold but even when I left it ticking over for ages, I still encountered that feeling of fuel starvation in that first couple of miles. After that, the engine ran much better.

I’ll drain some of the tank into a clear plastic bowl tomorrow to see if it does separate.

Never a dull moment....

Adam_Winstone wrote:My thoughts on initial query...

DO NOT ASSUME THAT THE FUEL YOU BOUGHT IS NOT THE PROBLEM!!!

As you immediately ran into problems post-fill up, with plumes of white smoke, this is exactly what I and others have experienced a number of times after filling up with contaminated fuel, typically contaminated from the pump (big name stations too!) and assumed to be diesel contamination.

An easy check is to empty the float bowl and fill from a different/new source. FYI - When I did this for a friend, it took a couple of kicks to start, then billowed white smoke (unburnt fuel in exhaust) then ran clean but started to die as float bowl emptied. We then flicked back on the fuel tap and the engine went from running well to lumpy and died quickly after. Draining the tank and refilling cured it, after we had stripped the float bowl again

A new issue so quickly after a refill... don't assume all is well.

I spent some time checking whether I hadn’t inadvertently filled up with diesel. It definitely isn’t diesel. It’s not got that slightly oily feel to it and it combusts, on the end of a wooden stick, like petrol not diesel.

I haven’t noticed any signs of water in the tank but I’ll have another look.

That said, I agree with you Adam. But what I can’t get my head around is that the engine did not stall when I blocked the tailpipe. I tried this at least twice.

I have the engine virtually ready to come out. I am minded to do this to (i ) check the drive side oil seal and halite washer and (ii ) have a look at the state of the top end.

Unless, someone can convince me that I definitely do not have a blown drive side oil seal.

You don't half have some interesting problem Paul

Re the seal if it wont let air out which is thin, it shouldn't let oil in which is thick and blocking the tail pipe ight not cause enough back pressure to stall the engine as slip joints are not airtight.

coaster wrote:You don't half have some interesting problem Paul

Re the seal if it wont let air out which is thin, it shouldn't let oil in which is thick and blocking the tail pipe ight not cause enough back pressure to stall the engine as slip joints are not airtight.

Hi, mate. It’s an AF Clubman. Nothing fancy and with no leaks at either end of the u bend.

If it was me I would strip and check the seal for peace of mind

Storkfoot wrote:

shamrockexpress wrote:I always had simlar symptons, after chatting to Ben at AF he pointed me towards the 8000 Motul oil i was using it turns out some of the race pre mix oils are very heavy and unless thoroughly mixed in a jar like at the racing, then they are likely to sink straight to the outlet in your fuel tap hence not mixing with the petrol until it has swished about the tank for a good while........
so i always had plooms of white smoke and lean running after filling with fuel, so the carb was getting a helping of 2 stroke and little petrol, solution was to make sure and always run injector oils instead of pre-mix!!!!
To note pre-mix has about 10% more lube than injector but only when properly mixed which aint possible in a tank.....not saying this is the case with all pre-mix oils but it was a problem with the motul 8000.

Maybe nowt to do with your issue but something to note.

That is really interesting. I am not using Motul 8000 but I did think that the petrol colour in my petrol pipe was rather red tinged (the oil is red). I have been using this oil but not for very long



Thanks for the reply.

I may still have a drive side oil seal that is blown mind. The engine definitely kept running, albeit badly, when I blocked the tailpipe.

Hi Paul,

I have been using that oil for quite a few years now in up to four scooters on the recomnendation of Darren Scott and never had any similar problems. Just thought it was worth a mention.

Rich'

Get a party balloon and fit it over your chaincase breather.
Start the engine. If it pumps the balloon, then you likely have seal or halite washer problems.

Don't try to identify or test the fuel, substitute at least a float boel's worth with different source new fuel. It is a very easy, quick and cheap test... takes about the same time as writing a reply.

You could easily be confusing 2 separate issues. Notdoig this simple test now misses out on a valuable opportunity... at least to rule it out.

Adam_Winstone wrote:Don't try to identify or test the fuel, substitute at least a float boel's worth with different source new fuel. It is a very easy, quick and cheap test... takes about the same time as writing a reply.

You could easily be confusing 2 separate issues. Notdoig this simple test now misses out on a valuable opportunity... at least to rule it out.

“Since then, I have taken off the flywheel, stator, exhaust and side casing so I could do a leak down test and, as I assumed there would be a leak, trace where it was coming from.”

From where I am, I may as well take the crank out and look at the drive side oil seal. I’ll look at the potential fuel and oil issues later.

Thanks for all the help so far. I’ll report back.

Does the white smoke stink badly?

Fast n Furious wrote:Get a party balloon and fit it over your chaincase breather.
Start the engine. If it pumps the balloon, then you likely have seal or halite washer problems.

Never thought of that, that's a brilliant idea.

Rich;

It wasn’t pleasant and it was definitely not the smell you get from two stroke oil. Bad smell though, perhaps not.

F n F;s party poppers idea sounds like a good one