1966 Super won't start

[gummybody]

Hi Gents, I'm in need of a pointer please. Was out last week on my Super when it suddenly started over revving, kill switch wouldn't stop it, pulled plug ( and turned fuel off ) and it still ran for around 5 seconds then stopped. Got it going again, albeit a bit lumpy and it cut out if I had to stop at lights but managed to get home. Thought maybe air leak but found throttle cable worn ( both inner and outer ) replaced inner and now can't get it started unless I put fuel straight into carb ( air filter off obviously ) it will then start and run for a few seconds then die again. I've had all 3 jets out and blown them, cleaned fuel and air filter ( they looked ok ) then fired air into small hole at top of float chamber and fuel came out of the small brass pipe and it started for a few seconds again. Looks to me like fuel starvation but might I still have an air leak? Have not taken carb off fully yet or checked gear oil for petrol but I have been changing idle screw \ throttle adjust. Don't like changing too many things blindly. Any other ideas please?

[alan34]

Hello there could be float in carb stuck open and flooded engine with petrol causing engine to race plus a number of other things but I would clean float chamber out and check float needle. it will be one thing crossed of list when sorted good luck and let us know how you get on cheers alan.

[gummybody]

Update on this, float checked ok. no petrol in gearbox oil. Removed carb and when sat on a mirror it rocked ( strangely from side to side rather that lengthways ) so, got it flattened out and fitted it with new gasket but no change. Won't start unless carb cleaner fired directly into carb with air filter removed. Any ideas gents?

[adrian]

Blocked jets

[alan34]

Hello there. Try putting finger over spark plug hole and turning engine over to see if there is suction if its poor could be rings or seals. If it fires when squirting fuel straight into air intake it sounds as though it's not sucking fuel in.or not getting through carb.let us know how you get on cheers alan.

[gummybody]

So this week changed Start Jet , Float , needle , housing etc for known good ones. Checked hole under Start Jet not blocked, new plug, good spark, finger over spark plug hole ( didn't suck but blew hard enough ) I can't 100% say the plug was wet ( smelled slightly of petrol ) but wouldn't start so no change. Dropped a bit of 2 stroke down air intake and started and ran a few seconds. Is there a way of checking fuel getting through carb to plug?

[alan34]

Hello there. it easy to take cylinder head off to see carbon build up and check piston movement could be a build up as you say it ran when switched off.good luck keep at it let us know how you get on cheers alan.

[L4NFF]

You have got enough fuel in the scoot? many of us have chased an issue that was an empty tank. Try take the carb box lid off and the air filter, open the throttle wide and kick the scoot over. You should see fuel getting sucked into the rotary valve. If not, then you may have a fuel problem. Carb out, clean jets and carb, check the filter behind the banjo arm and ensure fuel comes out of the fuel pipe when the tap is turned on.

It could however be that the engine got that hot that the plug ignites the fuel without a spark hence the reason it continued to run without a plug cap on. That should be evident on the plug as it would have been white. This suggests an air leak. Is the cylinder head torqued down? are the exhaust nuts tight? have the gaskets blown? This could also be why it may not start as the compression but have gone so it wont compress the fuel air and it wont drag the fuel air out of the carb.

Good luck.

[gummybody]

I tried kicking it over with throttle wide open and couldn't see fuel getting sucked into the rotary valve. Plug wasn't particularly white after the over revving episode? this week connected new fuel supply ( with fresh fuel )but no change, cylinder head nuts ok, compression seems ok. Spark fine. I suspect an air leak but will probably have to get someone to take a look at it. I have run out of ideas.

[alan34]

Hello there.regarding carb I would say you should see petrol getting through when kicking over with throttle full open shine a torch in to see fuel comming through with petrol on.if you cant see anything put your hand over air intake throttle open kick it over plug still in and see if it sucke palm of hand this might also suck any blockage out. if you dont see petrol it cant be getting from float good luck with it let us know how you get on alan.

[gummybody]

Hi - alan34 . I tried kicking over with the throttle open and yep, I could see fuel coming through. No suction when thumb over air intake though. Interesting thing is, next morning I could see 2 stroke fuel underneath the engine. It was in a strange / new place, roughly under the cylinder head rather than the usual place at the back of the carb. So, at least something to go on here. I'll take the head off and have a look there. I previously checked the cylinder head nuts and they seemed ok but haven't got a torque wrench. What's the thinking? Do most of you use a torque wrench or just tighten up the nuts in correct order? I'll let you know how I get on.

[adrian]

I always use a toque wrench 👍

[ironsloth]

Best get yourself an early Christmas present to yourself…

[alan34]

Hello there. I would take head off and while off replace the rings while head is off.sometimes you get a leak on the cylinder head as on my px there is no gasket just one at the bottom of the barrel.i always thought you might have ring trouble but it's only a guess so keep on trying you will get there cheers alan.

[gummybody]

Hi Gents, so took a while but had the Cylinder head off and there was like an oily residue on it which indicated a leak. Cleaned it up and it looks like new, piston and top ring look ok and no carbon build up on top of Cylinder head, barrel looks good too. So then re-torqued the head back on and with expectations high, gave it a few kicks. Back to earth with a bump as - no change. I used the open throttle trick and then put an eggcup full of fuel directly into the intake and it did start for a few seconds as usual. During this brief startup, I noticed smoke coming from around the bottom of the Cylinder head then found fuel dripping out lower down the barrel. Difficult to see exactly where but I think next step will be to take the Cylinder off and check \ change the gasket. So a bit disappointed but not done yet. I have had a quick look online at Cylinder removal, some say drop engine, other don't. I will have a read up but as usual any comments are gratefully received as it's not something I have done before. Either way, I will keep you updated.

[gummybody]

Hi Gents, I checked a few sites online etc and decided to remove the studs / exhaust then the Cylinder barrel. This went fine and Piston/rings/barrel all look ok. The gasket is the thin aluminium type, can't see anything obvious so I'll get a replacement gasket, some M7 nuts/washers/ spring washers and put it back together. I will lapp the Cylinder head first. Any advice please? Do you use gasket sealant and if so, on which surface?

[gpowell]

Have you checked flow from petrol tap?

Disconnect from carb and pull it out of carb box, you should have an uninterrupted steady flow full bore.

If the flow is poor or intermittent then take tank out and strip tap.

Ive seen the rubber grommet in the tap fail and block the holes causing restrictive flow.

[alan34]

Hello there this might sound strange but exhaust might of collapsed inside blocking gasses I know this happened to a friend of mine on a four stroke try kicking over and holding exhaust to feel pressure worth a try cheers alan.

[gummybody]

Hi Gents, I have now got the bits required to re-fit the barrel \ Cylinder head. alan34 - Exhaust is off at the moment so I'll try it first before attaching exhaust, gpowell - I did try with a separate fuel supply but due to fuel coming through with throttle wide open I have discounted fuel starvation ( for the time being ). Now I have to find the "pegs" on the piston that the ends of the rings line up with. They are not obvious ( at least to my eyes ). Do all pistons have these? Mine is a Pinasco 177 2 port.

[gummybody]

Update on this one, put everything back. Not too hard a job lining rings up with pegs and sliding barrel back on. Torqued Cylinder head back on and tried starting it...... no change, wouldn't start. Dropped a bit of 2 stroke down plug hole and re-tried. Started straight up for a few secs, so same problem. ( alan34 )This is with exhaust off. ( gpowell ) might have to look again at fuel supply. Trying to get it started again and ignoring the original problem of the overrevving ( engine screaming ) for now.

[gummybody]

Another update, I think I have found the problem. I took off the carb and carb box and shone a torch down the air / fuel intake. I could see that there had been a previous fix to the casings with something like JB weld and it has deteriorated and left what appears to be holes in the casing. Can't see too clearly without splitting the cases ( which I'm not sure I am up to ). So, that looks like it could be the cause of the over-revving that was the initial fault and why I'm not getting fuel drawn into the engine through the carb. So, do I try a JB weld type fix or split the cases to see exactly what we have got and see if someone can weld the case? I don't really want to change the cases even if I could get them. As usual, your thoughts are welcome.

[adrian]

Split the case's, it's not a hard job, just a little daunting first time. That's what I would do , and get them welded if needed, also good excuse to check everything else. Where are you based ?

[gummybody]

Hi Adrian, I'm in West Yorks near Cleckheaton. It's not long since the cases were opened. I had a Vespatronic kit fitted which needed new crank so seals were changed, Cruciform etc were checked then ( not by me), only done about 300 miles since then.

[adrian]

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