Cam-swap/engine won't start

Re-edit. The rear cylinder is now not firing again. I give up for the night.

i had a bad post.
Check carb rubbers
Check carb synch
Hope thats all.
Pod

Latest update, and all does not seem good.

Today I completely reset the rear cylinder timing - both cams out, and swapped back to standard exhaust cams. I was planning on seeing if this made a difference, but I noticed when I was turning the engine over by hand that I have a minor problem.

When the front cylinder goes through the intake/exhaust cycle, you can hear the air being sucked in through the carb. When the rear cylinder does...you can't. It sounds like air's being sucked in from somewhere near the engine. The carb rubber looks good, and covering the carb (and all the relevant hoses connected to it) generates no suction when turning it over by hand.

Any ideas? Blown head gasket (given that air can be felt at the back of the cylinder when it's running)? I'm out. Going to hand it over to the local shop, I think.

Edit: No, I've not checked the coolant/oil yet. I had a phone call that lasted 2 hours and I ain't going back out there now.

[5hort5]

Unlucky m8, if you need a hand with anything let me know (although I know two thirds of f all about mechanics but can make a good coffee and hold bits as needed)

If it's head gasket I don't wanna touch it with a barge-pole. I had a bitch of a time getting the heads off the knackered engine, and don't wanna have to do it on something that would matter if I broke anything.

head gasket is easy, its the base gasket that a pain in the **** lol, id do it yourself

Don't have the right tools...and I want to get a leakdown test done first before tearing it apart. My local shop will do that for me, and if it's burned valves or something else then I've got a spare engine here for parts anyway

What tools dont you have?

You can check the valves with petrol in the ports and watch for leaks (when the head off) if a little comes a bit of lapping needed, cheap to buy.

Been through this on my old bike, i enjoyed it.

Have nothing torque-specific. I get by with most things, but wouldn't consider dealing with engine gaskets without a torque wrench. Also, most of the sockets I have are 1/4in drive...and I snapped two extension bars taking the old engine apart because of the torque on the bolts. I'd rather get it looked at properly at this point

Well if you have the cash and want the piece of mind then i understand

Torque wrench is only £18, use a breaker bar too (vacuum pipe) i had the draper one tested and it was very accurate. I couldnt afford to pay for labour, so i bought a few tools instead. I had no prior experience either.

Good luck with it mate.