Not The Silencer Packing? - Help

[rossi]

Ok, here's the problem.

I have a nice tidy fantic 200 which I bought from the twinshock shop a few weeks ago. I have been going through sorting a few things out, tightening spokes, air filter, gear lever and silencer to front pipe seal. Nothing serious, just a few bits and bobs and the bike was running really nicely.

With the bike being a few years old, and the silencer showing no signs of ever having been opened to repack, I thought it would be a sensible move. I cut out a section from the inside of the can, cleaned it all out and repacked with silent sport loose packing. Not too tight but enough so I could lay the cut section of can on top of the glass and it was supporting its weight prior to welding the section back in. Bike starts and runs fine, nice and quiet. A few minutes in the street shows no problems.

Cut to the following week and a muddy trial. Bike starts fine and runs OK for the first few sections, but after a long hill climb between sections it starts smoking from the exhaust like crazy; then it coughs and dies. A couple of kicks and it starts up and completes the lap but with further problems with the engine stopping getting progressively worse. I tried a change of plug but after a few minutes it was back as before. All that seemed to help was running the bike with the fuel tap closed, opening it to let a little fuel through and shutting it again. Even this didn't help for long.

I have checked the plug etc and it is getting a spark. I am thinking about the silencer as it it the only thing that I changed between this wekend and the previous trial when the bike ran faultessly. Looking up the silencer outlets, the top one certainly has thick oily deposits which appear to be clogging the perforations in the tube, the lower outlet also but to a lesser degree.

Perhaps I have caused a problem by over-packing the can, or should it even be repacked as there was no packing left in there when I opened it? Is there anything else I should be checking?

Cheers

Edited September 9, 2010 by rossi

[t-shock 250]

What colour is the smoke from the exhaust?

Are you running a good quality full synthetic oil? What ratio?

Does the problem start when you are on full throttle?

Is the air filter clean?

[rossi]

What colour is the smoke from the exhaust?

Are you running a good quality full synthetic oil? What ratio?

Does the problem start when you are on full throttle?

Is the air filter clean?

Greyish smoke

putoline full synthetic at 50:1

problem started after a long uphill, at or close to full throttle. Once it happened the bike stopped running right. Next lap same again, top of the hill and it was belching out like it had a 60 a day chain smoking habit. each time it got progressively worse and harder to restart. It got to the point that I had to leave it for a while before kicking several times to get it going, until it gave up altogether.

Airfilter was cleaned and oiled when I got the bike. I have checked it and it is fine. Certainly no difference from the previous trial.

[chris morris]

bent carb needle or flywheel shifted possibily

[mrb505]

I don't know much about Fantics but I would think it's clutch side crank seals

It's best to replace both sides if you don't know when they were last replaced

[rossi]

To rule things out before I tear into the motor??

crank oil seal : drain the oil and measure what comes out. If it is 1 litre can I rule this out?

Flywheel : remove the left cover and have a look I suppose. I don't have an engine manual but do have the owners manual on disc from ebay. I think it has the procedure for checking the ignition pick up position. Can the flywheel actually shift on the crank?

I doubt it is a bent needle as it was working fine and and I have not had the carb apart to bend it in any way.

Is it possible that the problem was caused by repacking or am I barking up the wrong tree? Could a previous owner have adjusted the carb to compensate for an empty silencer; pack the silencer and it is then way too rich? What are the standard jet sizes? I think I read the needle should be 2 from the top, is that right?

Thanks again

[martinm]

Check the float needle valve ......the bit that shuts off the petrol supply when the floats go up. On the Dellorto, the float needles have a rubber tip, make sure its not split or fallen off.

This would explain why the bike starts and runs OK when you switch the fuel off, as you are stopping the constant flow of petrol into the carb.

Cheers

Martin

[rossi]

I had a closer inspection tonight. float bowl is fine, carb clean and in very good condition for a 28 year old bike; hardly a mark on it. The needle was in it's highest position so I dropped it down a clip but this isn't my problem as it is not even attempting to start now. I don't know how you recognise whether the flywheel has slipped, I wouldn't have thought this likely as don't they usually have a woodruff key to hold them in line? Not a massive spark, but it was there and blue so it is probably OK on the ignition side.

Anyway I drained the oil and only got 850 ml out so it looks like a set of crank seals may be required. I read in another post that you can get them out with the engine in the frame by filing a couple of spokes down into hooks. Do I need any special tools, eg pullers for the clutch and flywheel? I'm thinking that I might lift the head off and inspect the bore while I am working on the bike. Anything else worth checking while I'm at it?

Please excuse my ignorance; I'm more familiar with 4 strokes and, apart from replacing the power-valves on a kdx, I haven't really worked on 2 stroke engines.

Cheers

[blocky]

No packing in the rear silencer just 3 baffled chambers

[gumby26]

I just repacked my 'stock' silencer on my 240. The center is hollow and there is packing at both ends. I cut off both ends at the welds, then I used a torch to burn out the carbon and sandblasted the unit before I tigged it back together. I used Silent Sport to repack as my friend owns the company. The bike sounds as new and is snappier ! Pretty new to Fantics and all the posts I have read have been helpful, thanks. The bike is finished except for new badges and is the finest twin I've rode, ( O.K.,...my 84 SWM 240 is a pretty close second ! Will post a pic or two when the badges go on.

[bilc0]

Dont you just love these old sheds.

If electrics,carb etc etc are all original then there all be knackered or close to it.The harder you ride it the more chance one thing will fail the other thing.

Sounds like your having.

[rossi]

Thanks for all your replies.

Since the gear box was short of oil I called Bob Wright to ask about crank seals. Before I even mentioned the shortage of oil in the gearbox he said the symptoms pointed to the clutch side crank seal. Apparently the clutch side seal also fails more often than the flywheel side. I bought a pair of seals but will be keeping one as a spare. I won't do the flywheel side unless it fails.

It was a bit of a mare to get it all apart, but the interesting thing was the complete lack of marks from tools on the metal. I would say that I am the first person to have the cover off since it left the factory which probably explains why the weight on the end of the fly wheel was a pig to get off the crank. This, along with the general condition of the bike and the practically mint carb all points to a bike that has had very little use.

I need to get some more oil for the gearbox tomorrow. I'm also going to take the front pipe off and flush it through to clean out any deposits. Then it'll be fingers crossed time.

[rossi]

We have ignition!

A few nervous moments as it took a few kicks to get going the 1st time but it is now back to its normal 1 kick starting. It seems to run slightly crisper now thanks to dropping the needle a notch. Just got to get some pop-rivets the right size so I can mount the front mudguard that also got broken last time out and I'm good to go.