Soft Seize

[Littlewheels]

Rode my TV 175 to Weston Super Mare from Penzance then back after rebuilding the engine.

Wouldn't start after stopping for 5 mins - Plug cap loose!

Bogging down and backfiring. After strip down at side of road discovered condenser had failed. Added an external part and ran fine although the backfiring had caused the rubber air bellows to split.

On return journey:

Ran ok from Weston to Bude taking breaks to let the engine cool down. Then tried to do the last leg in one which was ok until we did a stint on the A30 for about 10miles. Ran it on full throttle but just before we were about to turn off it died. As I was running it in (800miles now) I rode with my hand over the clutch which I pulled in pretty sharpish. It was still ticking over when I stopped but turned off then pushed to exit. Started agin then rode to a safer location toilet it cool down. Rode the last 40miles and it ran ok as it did before.

Stripped down flywheel side to replace condenser and put clock on spindle to check it was running true. All ok. So question is do I take barrel off to check piston and bore or just be more careful until I reach 1500miles? Furthermore did the slit in the bellows contribute to the seize? Im running on 4% fully synthetic with a standard 20mm carb with standard jetting, original cylinder and Borgo 63.2 piston so it's actually a 180cc so would I benefit from a larger main jet?
Thanks

[coaster]

I think you have probably answere your own question, yes, a slit bellows will cause a weaker mix especially if the ambient temperature was on the high side. Oil ratios of 3 or 4% wont be the cause of a sieze providing the jetting as set up using the same mix. More important is varying you speed and not holding a throttle position for any length of time. Keep coming off the throttle every minute or so and let it 4 stroke for a few seconds especially important gpoin doen hill

[Fast n Furious]

Assuming air mix and ignition timing to be good, then you should take a look at how good your cooling system is, especially if you expect to run at full throttle for extended periods.
Have a look at this old thread for further advice.
http://www.ilambretta.co.uk/forum/viewt ... it=cooling

[Storkfoot]

I have a standard TV175. I used a new standard air bellows in my initial rebuild. The type with the valve at the bottom. I think it may have been a Casa one but don’t hold me to that. Anyway, on coming back from the C2C a couple of years ago, I had a soft seize and had to nurse the scooter home. At the time, I convinced myself it was because the tank was low on petrol, however, a few days later I noticed that the bellows had split. They were only a few months old

As I only had the one soft seize, which I managed to catch straight away, I haven’t taken the cylinder off to look. That said, it has not seized since. If it had seized a second time, I would have taken the barrel off and, at least, gently cleaned the barrel and piston up.

I replaced the bellows with the GP type incidentally.

Main jet size. I wouldn’t have thought that such a relatively modest rebore would necessitate an increase in main jet size. But, when you have the bellows sorted, it wouldn’t do any harm to chop and change the main jet, going up initially. Just to try it. Every engine is different, even standard ones.

Have you the standard paper air filter? I ask as I initially tried the MB metal mesh type. That let a lot more air in and made it difficult to jet. Actually, I just lost patience and put the paper one back in

Lastly, did you sus why the plug cap came off?

[Littlewheels]

Plug cap loose as the thimble on top of the spark plug came loose.

Yes I don't think i'm going to take the barrel off as it runs as it did before the seize. Of course I will change the bellows and going to check timing as I have to replace the condenser. May go one size up on the main jet to 104 and see what that does

[Storkfoot]

Plug cap loose as the thimble on top of the spark plug came loose.

Yes I don't think i'm going to take the barrel off as it runs as it did before the seize. Of course I will change the bellows and going to check timing as I have to replace the condenser. May go one size up on the main jet to 104 and see what that does

If you have adopted the standard TV175 SH1/20 jetting, the main jet was a 106.

[Littlewheels]

Yes sorry I meant 107