AR missing / 4 stroking at low revs

knobby · Post by **knobby** » 07 Aug 2007, 16:59

Help!! Only had the bike about a week and noticed that occasionally the bike runs very erratically at low revs. Not like that all the time. I've had the carb off, cleaned it out and jets blown through with compressed air. Checked the exhaust valve and it seems to move freely. Ran bike with AR cover off and valve moves when revs rise. Starting to suspect electrical fault but all symptoms are like a fuelling problem. Anyone had same problem?

mickstoy · Post by **mickstoy** » 07 Aug 2007, 17:10

im sure iv seen a posting about this before have a look through the old posts and see if you can locate it
good luck
does it happen when youve run through water?

knobby · Post by **knobby** » 07 Aug 2007, 19:44

Thanks for your response Mickstoy. No it happens in the dry. Can be running great then when you roll off the throttle and back on it's stuttering and missing. Also changed the plug but no difference.

Post by **Jonorow** » 07 Aug 2007, 21:10

sounds more like a jetting problem, suffering from lack of fuel on shut off, try a larger pilot jet. jon

mickstoy · Post by **mickstoy** » 07 Aug 2007, 22:45

as jon says it does sound like jetting is the bike running standard and is it still running standard jets? have another look at the holes in the jets if the bikes been stood for a while with the carb full of fuel it will go staleand leave a crud coating on everything, commpressed air may not be enough to clean it. try poking a nylon bristle through the jet and maybe fire some carb cleaner through it the holes are tiny and dont need much to affect them. when i bought mine it had been stood for about twelve months and it took four attempts on the carb to sort it out (it was running similar to yours!)
good luck

knobby · Post by **knobby** » 08 Aug 2007, 17:40

Thanks everyone for your help. I'll give the carb another clean using your suggestions. I'll let everyone know how I get on.

knobby · Post by **knobby** » 10 Aug 2007, 12:25

Removed carb. Found tiny pieces of black debris in bottom of float bowl which suprised me as I'd only just had the carb off a few days before. Pilot jet and main jet removed and blown out. Nylon bristle pushed through all clear. New fuel pipe and inline filter fit. Bike rebuilt. Took it for a test ride...... you guessed it no better. In fact if anything it seems worse! Gonna ring Leisure Trail and get a new pilot jet. Anyone any ideas?

Post by **Gwyn** » 10 Aug 2007, 15:28

[b]knobby :[/b]
> Removed carb. Found tiny pieces of black debris in bottom of float bowl which
> suprised me as I'd only just had the carb off a few days before. Pilot jet
> and main jet removed and blown out. Nylon bristle pushed through all clear.
> New fuel pipe and inline filter fit. Bike rebuilt. Took it for a test ride.
> ..... you guessed it no better. In fact if anything it seems worse! Gonna ring
> Leisure Trail and get a new pilot jet. Anyone any ideas?

Have you tried flushing out the petrol tank

Maybe sh** in the tank could be blocking the jet's and the fuel filter

knobby · Post by **knobby** » 10 Aug 2007, 16:05

Thanks Gwyn. Very little dirt / muck in the fuel filter. Think the black bits were coming from the float bowl seal. Someone had put sealant on there! Cleaned it off now. Rang LT and ordered the pilot jet. Chap I talked to suggested changing supressor cap. Just done that, seemed better at first but within a few miles same missing / stuttering fault appeared. Does seem to be at small throttle openings. Will wait now for the pilot jet to arrive unless someone comes up with something else to try.

mickstoy · Post by **mickstoy** » 10 Aug 2007, 16:28

have you checked the jet sizes to make sure they are correct to the manual and is the air mixture set up correctly the 1 1/4 turns in the manual is just a guide

knobby · Post by **knobby** » 10 Aug 2007, 16:51

Hi Ya Mickstoy. Jets are standard according to the manual. Just found a possible cause / fault with the air screw though. Found the O ring has perished, could be letting in air I suppose. I'll repair and try bike again. Thanks

knobby · Post by **knobby** » 11 Aug 2007, 16:27

Think we've sorted it! Put a new O ring on the air screw, had a test run but no difference. Put in the new pilot jet and went out again. Bike better but still sputtering at low revs. Air screw was set correctly at 1 and a quarter turns out so came out another half turn. Instant improvement. Out another quarter of a turn and I think I'll leave it that!! Best I've had it running. Thanks everyone. Special thanks to Mickstoy

mickstoy · Post by **mickstoy** » 11 Aug 2007, 18:05

no worries mate glad you got there in the end