TGB Hawk 50 won't run

[radddogg]

Excellent. Thanks for the detailed response.

After more research last night I also concluded it was fuel starvation. I'll do everything you've suggested suggested this afternoon and post up some pictures of progress.

Thanks

[bikenut]

Cleaning the fuel tank etc is a good idea said some posts ago. it is after all where the fuel is coming from.

Understand the fuel system and where all the pipes go etc..

The engine starts so that's a good sign.

So its a 2t, and the exhaust is oily ?

You will hear the reeds " play/vibrate", they are sprung flaps, you know of a saxaphone ?

How blocked is the exhaust i wonder, but go down the carb/fuel route. electric choke so there is a temp sensor somewhere. A parts book will help.

When it runs better, does the exhaust "hiss" and emit a "jet" of exhaust when the engine revs more, as if the exhaust is really fighting its way out or cant get out fast enough ??

Imaging maggy playing her sax when bart has stuck a sock in it !! :D
____________________
nuts about bikes

[radddogg]

[radddogg]

Ok, the exhaust arrived today so I had a good go at it. I took the tank off and have it a good shake up with fresh petrol. It was fine, didn't really need cleaning. I took the filter off and blew that through with compressed air. Took the carb off and cleaned it in fresh petrol and blasted it to within an inch of its life with compressed air. The jets and pets were all clear. I reset the pilot screw - all the way in then back out 3 half turns.

I fitted the new (used) exhaust - there is something metal rattling around inside it but shouldn't cause any issues.

So I tried to start it. After a short time I saw the filter filling with fuel and it started to cough and splutter. Eventually it started up with some light throttle but was struggling to stay running.

Thinking about the fuel starvation I wound the pilot screw out a turn, then another, and another and so on until it was about 10 turns out and I was concerned it was going to fall out. But it started to run a little better and with the idle air screw wound in quite far I managed to get it to idle, on its own, unaided!! I tried to rev it and it wasn't happy but slowly it coughed and spluttered and picked up the revs until it seemed to clear and actually revved up properly. I could release the throttle and it would idle then twist the throttle and it would rev up, although slightly laboured.

I could turn it off then turn it on first turn off the key. The idle was a little high and I thought maybe it was over fueling seeing as the pilot screw was so far out. So I screwed it right in to the base point and started it up. It very quickly died and wouldn't start. So I wound the pilot screw right out and it went back to running "ok".

I'm surmising that there might be an issue with the choke and what I've done is bypassed the choke by over fueling the pilot circuit.

So my next thoughts are to research and understand the choke system. I have tested the electric choke by running 12v through it which moved it out as I believe it should. Is there some adjustment in this? Maybe that needs setting up too

[radddogg]

I'm convinced there must be a vacuum leak now. That would cause these symptoms.

My money is on a leak on the intake manifold gasket. It looks like I have to remove the engine to replace it though 😑

[Sister Sledge]

You're getting there!
Seriously though having a machine like this will teach you a lot. Once it's all sorted and breaks again (it will) you'll know exactly what it is and how to fix it.

Exhaust rattle will send you bonkers BTW. Might seem like nothing now but it will grate on you.
If the engine's coming out (which it sounds like) remove the exhaust and tip and twist in every direction. Could be anything in there especially if it's a used pipe. I reckon it's the end off a pop rivet - found half a dozen when I rebuilt my Scorpion..
____________________
CCM 404 DS

[radddogg]

Ok so still no closer to resolving this. I thought I could diagnose a vacuum leak by spraying easy start around the inlet manifold. The idea is that you get it running on a steady idle then spray easy start around any suspected air leaks. The air leaks cause low air fuel ratio so spraying easy start causes the vacuum to draw in the East start and cause the engine to surge. I tried this but no luck. Made no difference. This could be a good thing though I suppose.

So here is a clip of it running now. The pilot screw is all the way out and the idle screw is all the way in so clearly there is something way off with the fuelling. It seems very hesitant too but maybe that's just how it should be?

Only thing I can think to check now is compression. Any other suggestions or comments?

Video clip attached

[bikenut]

It may be the audio recording but is the engine making "rattly/knocky" noises.

It runs and revs pick up.

You have access to parts diagrams/exploded views ?

I assume there is no "prime" position on the vac tap ?

The vac tap must work as its letting past fuel, but the diaphragm in it may be leaky/air.

The camera is waving about a bit in the vid and some stuff is difficult to see, no smoke seen but there is some red fluid in the 2t oil tank yes?

The air hose worm drive clips seems to be in the wrong place where it clamps the air hose from the air filter to the carb intake, strangling it a bit perhaps?

Would suggest taking the carb off again and soaking it in a mixture of the red ex fuel cleaner and petrol, leave for at least a day and then test to see that all the carb passages and very small holes in the carb jets, the ones in the main jet emulsion tube etc. are all clear. Compressed air is good but you cant really see that, so try squirty carb cleaner using the small diameter tube they come with, or an oil can........the small hand ones that you pump oil from, messy I know but you will know that all the jets etc ( as the tank ) are all ok.

There seem to be 3 tubes going to the carb, one fuel, one vac to tap and one from carb body slider area to oil pump ?

You have a wiring diagram for the choke ? Or find/follow the wires from the choke ( "solenoid " ? from the carb..........
____________________
nuts about bikes

[radddogg]

Thanks for the in depth reply bikenut. We will get there in the end. The house clip on the air box is undone so wouldn't cause any major issues.

Ok, after thinking more last night. I thought it must be drawing air in somewhere. So I thought crank seals. Whipped off the variator cover and found some dampness along with the remains off a rubber seal. I'm guessing this is part of the problem.

The reason I say part is that there is obviously more to this as I ran a compression test. Not good. 48psi 😥 and it wouldn't hold that either. I sprayed some WD-40 into the cylinder and it raised to 60 and held it there.

I doubt crank seals alone would cause the low compression so I guess it's time to remove and strip the engine!

video attached

[pbt]

TGB 2ts run like dogshit with a missing/damaged airbox

[radddogg]

[radddogg]

So I stripped it down and the piston and cylinder weren't too bad. But the engine has been apart before and reassembled by the chuckle brothers by the looks of it. The cylinder gasket has been replaced with a piece of old corrugated pizza box and smeared with silicone, completely blocking the side ports. I have no idea how it managed to run like this. Explains a lot. I've ordered some seals and gaskets and will see what difference that makes. Enjoy the photos!

[Sister Sledge]

Kin ell that's hilarious! What next? Plywood gaskets??
I can see a few small dings atop the piston - be sure to check for said pieces - just in case.
____________________
CCM 404 DS

[cb1rocket]

That my friend is a full rebuid.

Wtf!
____________________
Honda H100S2 Rebuild - https://www.bikechatforums.com/viewtopic.php?t=253852

[bikenut]

Oh what fun.......

time to learn how to make gaskets perhaps.....any pics of the side of the piston etc....

It does not look as if the engine has been "split", but how are the rings and bore, measurements and ring gaps, are the rings "narrow" in places or even all the way round, how is the little end, big end and mains??

You say you have seen some "damp" by a main bearing seal, please post a pic......

Can you get parts diagrams, they will only help you.
____________________
nuts about bikes

[radddogg]

Hi

Actually it does look like it has been split. There is evidence of more silicone sealant between the two crankcase halves.

I'll buy some gasket paper as I'm not throwing £8 on a genuine gasket. Can I trust the head gasket? It's looking pretty flat and has clearly already been reused.

I didn't get any pics of the side of the piston as it looked ok, a few minor scratches but nothing that would cause a drop in compression. The rings look good too.

The little end looks good. The big ends were a little notchy but not noisy and that could be partly to do with the stator affecting the smoothness. Any tips to removing the flywheel? I used a puller on two bolts and they started bending. Might have to shock it.

I've got a Haynes manual for Chinese scooters and it does list TGB but not explicitly the Hawk. Some of the pictures are relevant, others aren't but it's enough to get me by in the main.

I've attached a couple of pictures of the variator side. Will have to strip it completely but am away with work for a few days now. Also next weekend I'm planning to swap the gearbox in my T4 for one I've just rebuilt so might struggle for time on the scooter, although I hope not as I'm finding it fun and interesting getting to know this little two stroke.

[cb1rocket]

you have got to spend proper money fixing that. No good doing a half arsed job. Sorry mate, thats a total strip down
____________________
Honda H100S2 Rebuild - https://www.bikechatforums.com/viewtopic.php?t=253852

[bikenut]

Can you link in some parts diagrams and exploded views....i do not know this bike.

Head gasket, is it a copper ring?

Picture of flywheel,you should use a proper extractor, same with variator etc., but parts exploded views can only help.

You will know why special tools/bespoke tools are needed, having re assembled a t4 box.
____________________
nuts about bikes

[radddogg]

Hi

I stripped it right down and split the crank case. I found why the engine has been stripped previously. The crankcase had witness marks where the crankshaft had scored it, presumably due to a failed bearing. I guess at some point it was run without oil.

So I rebuilt it, replacing the seals and turned it over to test the compression. The compression test was still low at 48psi. I couldn't understand as the was no obvious reason for it. So I used the push fit attachment on the compression tester rather than the screw fit and got 108psi. Tried the screw fit again and it was low again. So looks like the screw fit is faulty and I probably didn't need to rebuild it 🤪

It was a good learning experience though.

Tried to start it and it would start. Checked for spark and nothing. So something has gone wrong since I pulled it apart. One for another day though as my priority is putting the gearbox in the van.

Any ideas welcome though. Thinking it might be something to do with the stator as I had to remove that to split the crankcase.

[bikenut]

pics, of the stator and flywheel, you used a proper "puller" not the 3 legged variety, but you have assembled a t4 gearbox so should "know".....
____________________
nuts about bikes

[radddogg]

[bikenut]

So no obvious "puller" points apart from say 3 or more threaded holes for the fan, maybe the oe tool is a plate that bolts to the flywheel via these threaded holes, with the plate having a central nut and "bolt", the bolt being the part that pushes against the crank end and pulls the flywheel off. A similar arrangement/tool for outboard motor flywheels, lawn mowers and stuff like that.

You have not "bent" or damaged the flywheel ??

The stator is usually "static" and screwed to the engine, a picture would confirm.........you have access to parts diagrams/wiring diagram??
____________________
nuts about bikes

[radddogg]

Yes it's a static stator. I don't think I've damaged the flywheel. I'll strip it down and check though.

[bikenut]

It had ht before, so have you done any painting, or trapped a wire/bad connection ??
____________________
nuts about bikes