Starting problem, any ideas?

i havent done anything since totally stripping and cleaning the carbs last saturday (see Neka's GPS thread for where we went). I got a lot of shit out of the carbies and went through most of a can of carby cleaner. This having been said they were looking rather tidy before, and using the tube on the can nozzle i managed to force clean a LOT of crap out of the idle air/fuel tubing.

Will try and go back and fit her back up and give her a burl this arvy.
Thanks for any/all suggestioins, btw gos, the vacuum tap seems pretty good, so far...

Still didn't start this arvo, i have all but ruled the carbies out as a problem (unless they are pretty fucked up, but even then i managed to force carby cleaner through EVERY orifice on the carbies.

Am going to have to pop by a bikeshop and buy the correct plugs as per the above, also might have to invest in a timing light.

Have you tried pulling the plugs out, and kicking it over with the plugs pressed against the head, to check the spark ??

You want a Big Fat blue spark - anything less may indicate problems with ignition......

one step at a time grasshopper...........

pulled the RHS plug out and the spark was healthy bluish with a white/red core. So plenty of voltage there.
Got hold of a pair of new plugs and a timing light from supacheap this morning (actually got a decent one, not the cheapass ones that use a neon globe),

Will swap the plugs once the battery finishes charging and check the spark on that, then the timing and hopefully replacing the plugs is all that was needed.

ok, to add more confusion a.k.a fuel to the fire, tonights effort.

I'm DAMNED sure the plugs are getting a little wet when im running the choke. The very act of squirting a bunch of carby cleaner or aerostart down the carbs (even better is a little squirt down into the screw hole meant to be used to balance the carbs) gets a slight cough of life, and without the aerostart the bike occasionally will stumble along when the starter is being pressed like it is trying to cough into life. But it never quite gets there. given how many times ive taken the carbies out and how well i've managed to clean them out progressively im reasonably confident in my carby stripping/assembly abilities.

The spark plugs on both sides were swapped with brand spankers of the correct heat rating (ngk d8ea's) and ive tested them outside of the barrel, a very very healthy blue spark appears each and every time.timing light shows everything appears to be set up correctly.

Compression sounds pretty decent, though im starting to consider getting hold of a compression guage to actually verify what is/is not there, anyone here nearby got one they can possibly live without for a fortnight or so? I just want to make sure that compression is not an issue. Also another thought is if the compression is down, perhaps the rings are sticking (the bike WAS unmoved for uhm, about 18 months before i got hold of it so this is a distinct possibility) i should get hold of some of that subaru top end cleaner and squirt a bit down each of the cylinder heads and leave it for a couple of days and then spin her over and see if it makes an improvement.

Any more ideas? aside from bin it (trust me, im considering this option the more of a bastard it becomes to start)

How does the fuel flow out of the fuel tap? When I first got the AG100 I had to clear several tons of crap out of the tank and clean the fuel tap just to get decent flow.

If the motor runs on cold start and the spark is good my guess is a fuel/air issue. Assuming the carbs are Ok, start at the top and work down. Fuel tank to carbies, air filter, breather lines, fuel filter etc. On the AG fuel tap it had a small bowl with a mesh filter in it, and years of crud was built up in the mesh blocking the fuel flow. Silly question - how much fuel is in the tank and how old is it?

Just another thought to add to the confusion, what's the condition of your carb boots? Maybe you're sucking a bit too much air in

How does the fuel flow out of the fuel tap? When I first got the AG100 I had to clear several tons of crap out of the tank and clean the fuel tap just to get decent flow.

Perfectly well on the vacuum only tap, the one with prime seems farked, which is a shame, but i've worked out how to prime the tap efficiently on the vacuum only one. I have also taken the fuel tap right apart and cleaned it out (it was grotty and full of rust powder)

If the motor runs on cold start and the spark is good my guess is a fuel/air issue.

Im not really even getting a cold start beyond pumping it full of aerostart and hoping for it to run beyond five seconds at the best.

Assuming the carbs are Ok, start at the top and work down. Fuel tank to carbies, air filter, breather lines, fuel filter etc. On the AG fuel tap it had a small bowl with a mesh filter in it, and years of crud was built up in the mesh blocking the fuel flow. Silly question - how much fuel is in the tank and how old is it?

Carbs have now been stripped 4 times, each more thorough than the last and i am 95% confident of them not leaking & are now no longer full of crud. I have removed and cleaned the grime out of the needle float mesh filter, there was a bit there. Needles, jets, EVERYTHING has been given a clean and a visual once over and are now at factory settings (and from looking at it is in actually very good nick).

Fuel bowl's are now filling with fuel quite happily and im moderately confidant fuel is drawing through as i *think* the plugs were wet. Next i am pulling the plugs again and this time running it with a compression tester (got one from supacheap, just got to convert an old sparkplug into a threaded adapter). When i've done this (and assuming the compression isn't up the shit) im going to make sure the plugs are clean as a whistle and then spin the engine over a few times and check the plugs to see if they are getting fuel on them.

Just another thought to add to the confusion, what's the condition of your carb boots? Maybe you're sucking a bit too much air in

Carb boots are firm but not hard, which i guess is what you want. No tears in them from hamfisted reinstallation attempts (which is amazing given the abuse i've already subjected them to. Also the diaphragms on the carbies are also in rather spectacular nick, internally the thing looks near brand new, which is fortunate, given the external appearance of everything.

But as above, once the adapter has been made im having a go at checking the compression and then going from there.

What about the top end? If fuel is getting through carbs and you have a spark, valve opening could be an issue? If the bike sat for so long Valve seals could be shot? That could show up as part of the compression test.

hence why im doing the compression test. Will do one dry and if its under 110psi (i figure thats reasonable given it should be 125-140psi with its 10.5:1 compression ratio) ii'll be doing another with a shot of moderate viscosity motor oil down the spark plugs. If it turns out that motor oil is required and DOES improve the compression ratio, i might go down the avenue of acquiring some subaru upper engine cleaner and dosing it down the spark plugs and see if that improves things in the long term.

Ran the compression test this evening, got 140-145psi on the left cylinder and slightly worryingly lower 120-125psi on the right hand one. I put about 10-12ml of engine oil down the right cylinder and the next test ran at about 140 on that one. So its lower on the right, but it isn't quite low enough for me to start freaking out about having to replace pistons, rings or get oversized rings. That having been said i saw a set of rings for it on ebay and i think i might get them simply for the whole "well its only $40 and it may be a bastard to get another set so cheap if i ever need them" factor.

So the test went reasonably well, and out of curiosity as i had the plugs out i put a squirt of carby cleaner down both plug holes and she fired first shot and went for about 4-5 seconds or so, which implies to me that that there's nothing wrong with it ignition or compression wise.

As the floats have been set to the correct height and the idle jet is set to the factory specified 1.5 turns out, my next move is to wind the idle screw out a half turn on both carbies and give her another half dozen cranks to see if richening it helps (i mean it sounds like its almost catching currently). I'm thinking this as its still possible theres still crap in there clogging it so it might be worthwhile turning it out a bit to see if that helps as its a lot better alternative to stripping the bastards a fifth time.

Progress!!!

The carbs came out tonight and i have stripped one of them and used compressed air to clean the passages out. The mains were fine, as were the fuel jets and the choke fuel pickup. However the idle air passage sounded like it was blocked for the first four or five quick squirts of air through the pickup at the carb mouth, then it sounded like it cleared and i could hear the air exit out of the idle needle screwhole and the venturi. So this may have been my problem with clearing her out. I'll give it a once over again tomorrow morning when i have a few hours to fiddle with the thing and will clean carbie #2 out in the same way.

Thanks once again for suggesting the compressed air as that seems to have done the trick, im just hoping like hell that this fixes the issue and this is the last time the carbies have to come out for a long long time.

Good news Mike, I hope she fires up now and you can concentrate on some of the other stuff you need to do to her...cos I'm sure there'll be plenty more after the carbs are sorted, it's an old bike after all

Good news Mike, I hope she fires up now and you can concentrate on some of the other stuff you need to do to her...cos I'm sure there'll be plenty more after the carbs are sorted, it's an old bike after all

You and me both,and you're not half wrong about extra things to be done, i have a tank to strip back (external pretty up) and kreem (internal not so pretty work), spare forks i might swap the uppers on at some point, rear brakes to do,lots of shiny bits on the engine to polish, give the electrics a good once over, not to mention new rubber hoops.

So yes, plenty to do, just a shame i just got stuck on this bit for so devestatingly long.

Wrote this last night, but my net was borked, so posting it today.

Ok, carbs were taken out again and i've verified that there's not anything blocking the passages now from either the fuel or air jets. However im not sure if it'll start, it had a bit of a charge, but wasn't quite cutting it before the battery went flat. I pulled the battery and dropped it on the trickle charger to sort that as a worry.

But if that fails, does anyone have a clue wtf do i do now to get this f*#*$&%ing thing to start? The battery will go back in tomorrow afternoon and i'll give her a crank,but imtrying to think of what else may be screwy if this doesn't sort it out.