83 GS450TX Won't Start

[Guest]

Hello all. I have aquired a new steed,(FREE 83 GS450TX), in the stable. Right now it's a little lame but with the help of you guys here I'm sure she'll be a "Kentucky Derby Contender".

Here's the skinny,

1) Dipped the carbs in Berrymans overnight, can now blow compressed air through all passages, with special attention to the pilot circuit.

2) New needle and seat with o-ring

3) New o-ring on pilot adjustment screw set to 2.5 turns out

4) Float hight adjusted to middle of factory settings

5) Has decent spark

6) Compression is approx 140-150 on both cylinders

While cranking it over it will lightly putter through the exhaust while holding the starter button but as soon as you try to give it fuel, either by turning the throttle or adding the enrichment valve, it will backfire through the carbs. With the signal generator cover off , I can see the rotor actually turn backwards when it does this.

Kind of lost here. Being a car guy, it acts like the timing is off, but it has the whole electronic deal on it. The signal generator plate can only fit on one way so it can't be that. Even swapped the plug wires in case someone had misswired the coils, they didn't. I took the rotor off to be sure that wasn't fooled with, and it wasn't. Put a set of Dyna Green coils on to see if the coils were bad, they aren't.

Not sure where to go from here. I need your help please.

Thank you in advance.

Don

[pete]

Hey Don, free is a great price!

Have you checked to make sure you're getting spark properly? Spark plugs sitting on the head or something?

If it's an '83 I think that means it has electronic advance, although I have a feeling the TX in '83 was still the equivalent of the E/S/L's from '82 so may have mechanical advance.

The ignitors on the 80 - 82 450's seem to be quite prone to failure at this age so if it has mechanical advance and one of those ignitors, grab the Clymer off BassCliff's site and do the tests.

[don]

Thanks Pete,

Yes have checked spark with plugs grounded to head via alligator clips. I like useing them because you can get the teeth through the paint and gook on the head. No question it's grounded.

This 83 was mfg in late 82 but has all electronic ignition. No mechanical advance.

I have the manual from Cliffe's site and have done the tests. I don't trust the tests though. On my 83 550E all of my ignition components are verry simillar and fail those same tests but the bike runs like a top. Starts on the first crank and pulls right to 10-11k on the tach. Either I'm doing the tests wrong or my meter has the wrong internal impedence or something.

Thanks again for the help.

[pete]

Hmmm... how's the intake system? Airbox all good and sealed with a good air filter?

[Gorminrider]

Try a timing light?

maybe just checking the valves,too. I wonder if someone has had the head apart and got the camchain all wrong before they sold it to you?

[don]

OK. Really didn't do mutch of anything besides fiddleing with this and that since my last post. Basicly kust double checking everything I've allready done. Tried it one more time and...........POOF.........it runs. Don't know what the hell I did different this time from the last 300 times, but it fired right up without that backfire thing.

Once again thank all of you for your gracious time and thoughts to help me.

Don.

PS

Now I can lower it into the cellar through the hatchway and get to work on it knowing I don't have to tear the engine down. WAAAAYY COOOOOOL!!

[barnbiketom]

Sometimes when they sit for a long spell, they just won't run ..I think due to crud accumulating on the valves, and the rings taking a set. I know it had compression, but its running now and hope it stays that way!!!