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carb
Mar 3, 2007 16:42:03 GMT
Post by breezer on Mar 3, 2007 16:42:03 GMT
Took prim out for first ride of the year, it been sat in the garage and started up every now and then.
Went like a dream until suddenly revving its tits off, not slowing down when I shut the throttle off. Wouldn't shut off from the kill switch. Had to stall it.
Started up no problem, until I gave it a decent fistfull then it started again.
Don't think its an air leak, my guess is that the carb has got a bit gummed up while its been sitting. Its a dellorto PHBL
Is this something that will clear itself up with a bit of riding, or does it need a full strip & clean?
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carb
Mar 3, 2007 18:42:12 GMT
Post by Juan on Mar 3, 2007 18:42:12 GMT
Don't piss about Jim,strip it right back and clean properly with carb cleaner and rebuild with new gaskets.And check the float isn't sticking/damaged while you're in there.
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carb
Mar 3, 2007 18:51:52 GMT
Post by breezer on Mar 3, 2007 18:51:52 GMT
Does it sound like a sticky carb to you? or do you think it could be anything else?
Anyone got any experience with PHBLs?
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carb
Mar 3, 2007 19:10:55 GMT
Post by Juan on Mar 3, 2007 19:10:55 GMT
Sounds like an air leak to me but I'd haul it down for a full service anyway,it could be a couple of things.Not a huge expert on carbs but inspect your rubber mount too,they're prone to cracking/splitting.
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carb
Mar 4, 2007 12:47:42 GMT
Post by jonnysnatchsniffer on Mar 4, 2007 12:47:42 GMT
also check your cable is ok and the throttle bar in the headsed isnt gumed up
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carb
Mar 4, 2007 18:07:21 GMT
Post by breezer on Mar 4, 2007 18:07:21 GMT
Took carb out today to have a look.
Float is free and rubber maifold connection is fine.
Cable feels free (as when I shut off the throttle there is no slack)
It runs fine at low revs, its only when I give it a fistfull of throttle that the problem starts.
How do I check for an air leak?
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carb
Mar 4, 2007 20:48:31 GMT
Post by ets on Mar 4, 2007 20:48:31 GMT
Definitewly an air leak. After you've checked the carb and it's fine then you need to check the oil seals. One of my scoots had the same problem. If it is the oil seal flywheel side it would rev up constantly.
A quick way to check is with the engine on idle, unscrew the oil loading plug bolt and if the engine revvs up then it definitely is the oil seal clutch side. Sorry.
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carb
Mar 4, 2007 21:10:02 GMT
Post by breezer on Mar 4, 2007 21:10:02 GMT
Are you saying if its the flywheel side it wouldn't tick over at ANY point, it wuold just start revving straight away?
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carb
Mar 4, 2007 21:58:37 GMT
Post by ets on Mar 4, 2007 21:58:37 GMT
Correct. The one on the flywheel side, if damaged, lets air in and you hardly get a tick over. It's relatively easy to change it if necessary, it can be replaced without splitting the cases, only take the flywheel and the stator off, pull the old one off and push the new one in (grease it lightly to ease the process ). On clutch side instead the engine is still air tight and air will start leaking slightly only if you rev up the engine. If you take off the oil plug on idle it's going to rev up straight away (if the oil seal is damaged) 'cos air would start flowing in big time.
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carb
Mar 5, 2007 6:45:30 GMT
Post by breezer on Mar 5, 2007 6:45:30 GMT
Bugger bastard twat bollocks. Cheers ETS, will give thata go. Hopefully it won't work...
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carb
Mar 5, 2007 8:47:23 GMT
Post by breezer on Mar 5, 2007 8:47:23 GMT
One thing though... (I've been thinking about this...) wouldn't opening the oil fill hole make ANY bike rev higher - not just those with a worn clutch side oil seal?
Or is there some mechanical say-so that overrides my thinking?
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carb
Mar 5, 2007 12:30:39 GMT
Post by ets on Mar 5, 2007 12:30:39 GMT
It wouldnt rev if the oil seal is tight. It has no reason to.
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carb
Mar 5, 2007 18:10:13 GMT
Post by breezer on Mar 5, 2007 18:10:13 GMT
OK Cheers, not disputing, just didn't understand the principle behind it.
Jim
Been told another way to look for air leak is to start bike up and cover the exhaust pipe. Apparently if it DOESN'T have an air leak it will cut out sharpish, if it does however it will continue to run.
Does that make any sense?
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carb
Mar 5, 2007 19:00:44 GMT
Post by ets on Mar 5, 2007 19:00:44 GMT
Sort of. It'd make some sense if the leak has to do with the cylinder itself, more exactly if the leak is from the head. If the leak is from the case blocking the pipe wont tell anything.
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carb
Mar 5, 2007 19:57:57 GMT
Post by breezer on Mar 5, 2007 19:57:57 GMT
o-kay... kicked bike up, sat at tickover, blocked exhaust, and it cut straight out. kicked bike up again, sat at tickover, removed oil fill plug, bike just sat at tickover and spewed oil all over the place (wasn't expecting that! Can't see any visible traces of petrol in oil. Back to thinking its a carb problem unless an air leak could be triggered by the engine getting warmed up...?
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carb
Mar 5, 2007 20:15:50 GMT
Post by ets on Mar 5, 2007 20:15:50 GMT
Shouldnt really spit oil all over the place (probably some drops too many in the case) but now you know the oil seal and the cylinder head are fine. Back to the carb now. Check the manyfold is bolted properly on the case and the gasket isnt damaged, I would also take te carb apart and clean it properly, best way is to blow it with compressed air, I have also used wd40 and it did the job. There's nothing else I can think of....
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carb
Mar 7, 2007 21:56:35 GMT
Post by smallframesdotcom on Mar 7, 2007 21:56:35 GMT
It's a carb air leak if you can cure the mad revs by pulling the choke out.
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