Hitchcocks Forum

hi all,

i am doing some winter fettling on my 1960 super meteor. Main job is to get it re-bored but a problem i have had for a while now is the plugs getting sooted up very quickly and the bike then starts to misfire before very quickly dying completly. i have tried to drop the needle jet clip to the top most notch but this has made no difference.

i have been investigating the carb today as i have noticed when tickling the carb, when full the fuel doesnt come out the the tickler, instead it drips from the hole in the underside of the carb splitter manifold.

i have found that the main jet in the carb is a 250. yet i have another carb here from a SM engine and the main jet is a 240. can someone please tell me which is the correct jet to have in the carb. os it either of these or is it a smaller one still.

many thanks
ed

Main jet should be 240 but it isn't your problem as the main jet only works fully when flat out, so won't have an effect at tickover or moderate speeds. A 5% increase in main jet is negligible anyway. If you are re-boring, is it possible the sooting is burning oil? You don't say what carb you have (general note: can folk please include all relevant information to save repeated posts to identify small details?) but if not oil burning I'd be looking at throttle slide or maybe leaking float as symptoms are more like fuel flooding.
REgards, Mark

hi mark,
sorry i forgot to mention it has a monobloc carb fitted. how can i check if the float is leaking please. i know on a standard concentric carb it is easy to check but not sure how to go about it with a monobloc. when you say it could be the throttle slide, do you mean is it worn? The soot could be due to oil burning but i would have thought the plugs would be quite oily if this was the case not sooty. is this right or not?
When it starts to misfire due to the plugs it normally starts when i am riding at speed and gets worse rapidly. causing the engine to loose power before cutting out. as soon as i put a clean set in it fires up again perfectly for a few more miles. i do think that 99% of my problems are due to the bores being shot. they are at +.40 at the min so i am going to buy a new pair of pistons from our hosts and then send the bores for rebore by a company recomended by hitchcocks (the name escapes me for now), hopefully once this is done the bike should run beautifully. thanks ed

just a quick note to add i have just done a compression check on the bores and i am getting about 90-110psi from a cold engine. i know the bores should be warm to check compression but does this sound about right? i would have thought a reading of about 150psi would be about right. thanks ed

Barnes, your standard carb settings should be slide 3 and a half, pilot jet 30, main jet 240. All these details are from the 1960 Super Meteor Parts Book which you can find here on this site (sidebar to the left of this page). It doesn't sound like your carb is worn. All in all I think I'd get the rebore done first then see if the problem persists. Light sooting can be oil burning, after all petrol and oil are both derived from the same source so can look similar on a plug!
REgards, Mark

Thank you for your help mark. I hope i dont sound too thick here but what do you mean by slide 3 and a half. Thanks ed

Throttle slide, should have 3 and a half stamped on it's top surface where the cable is clipped in. Why are you re-boring it if you haven't measured the bores yet?
REgards, Mark

hi mark, thanks for explaining the float markings, i do have a 3 1/2 float installed. i am re-boring it without measuring due to the very high level of combustion gasses i am getting in the crankcase, the engine developed a large oil leak around the breather and when i took a pipe off this upto the air box where i fitted a catch bottle. the bottle filled with 500ml of oil within 25miles. along with la large amount of vapour escaping. i have put this down to the pistons. am i right in this assumption? i have removed one cylinder head and contrary to my previous posts the bike is running std pistons so will take it to +20. i must have been getting it mixed up with a previous engine i have worked on. sorry. thatnks for your help. ed

Barnes, it's a 3.5 slide, not float. As a matter of information, all the Twins breathe hard, DON'T rebore it until you have investigated other options, eg improved breather, reduce oil level in tank etc. You can easily check if it's a breather problem by leaving the filler cap off and running it for a while. In the end it could also just be a badly assembled engine and leaking as a result! That is all... REgards, Mark

Have you checked the float height?
Here's how;
http://www.whfolk.co.uk/REOCHUMBER/Arti ... nobloc.htm