P2 running rough

[stonerosesmod]

My P2 developed a bogging down off idle and through the gears,so I replaced the carb with a new one and a 120 main for the simonini.Seemed OK and was running ok when cold last weekend,but on the way home was starting to idle high at junctions after a long run when it was hot.It also was pinking lightly along a long duel carriageway then near home it wouldn't Rev off idle unless the choke was out regardless of mixture screw setting.
Got home and just checked and flatted off carb box bottom and carb,stripped and cleaned carb (all jets clear and clean) and refitted tightly with new gaskets.Started ok but still reluctant to rev clean from idle,it just bogs slightly unless choke is out.Its on a sidestand but when the engine bogged and died,it spat gear oil out of the breather down the side of the engine! Timing is retarded just past the A mark and all standard jetting apart from the main jet.Possible main oil seal leak? It doesn't smoke either?

Any ideas or further checks I can do?

[mick1]

By needing the choke indicates lack of fuel...lack of fuel could also be the cause of the pinking. I'ld look at the fuel flow and check the banjo filter......could be muck in the tank/fuel tap needing cleaning...........

Thinking on....if the main oil seal has gone that could be sucking too much air in and the choke compensating by adding more fuel....?

Probably go for the tank/tap option first as it's easier...

[Muttley McLadd]

Is new carb a bgm one?
Check the float lets it hold more than a teaspoon of fuel.

[stonerosesmod]

Was a dellorto carb,well a 'genuine' new one! I'll try the fuel flow next but tank cap is clear and still bogged down when I removed it.

[Muppet]

rings?

[Padge]

kinked/collapsed/blocked fuel pipe causing fuel starvation, but if pulling choke makes it run better I would think carb is getting/holding enough fuel, so suggests an air leak to me, things to check (in no particular order) main oil seal (drain oil and check for petrol in oil, also that there is still oil in it) flywheel side oil seal (pull flywheel and look for signs of leaking around seal), if engine has been ported, check it hasn't gone through casings round the transfer feeds as most of the time you break through the casings and people repair them with chemical metal/JB weld etc and can be prone to leaking, carb overtightened and warping, air leak at cylinder base/head, exhaust leaking and drawing air etc ....
just a few things to try

[stonerosesmod]

Cheers all,will drain gear oil this weekend.

[gaz_powell]

It's probably drive side seal, I ve had the same symptoms before but I had the symptom ones before and stripped the motor only to find all fine but changed seal while I was there only to find the same when rebuilt. Turned out to be spaco carb, replaced it and sorted.

Didn't know BGM were doing SI carbs ???

[rosscla]

I had something very similar. Would run with the choke out but was really hard to get to tickover if not. Would die if you coasted down to a junction.

Eventually the drive side seal disintegrated and wrecked the top end. I think it was loose in the casing and leaking air.

[stonerosesmod]

Before I strip the engine,would it be worth getting it running then spraying the outside of the casings with soapy water to see for any hairline cracks? Would that work?