Grognor's / balls of flame

650rider · WebMaster Joined: Feb 09, 2005 Posts: 431

I'm trying to rebuild a '78 xs650 that's been sitting for about 10 years.
I've put most of it back together, but the best I can manage to do is get it to blast balls of flame out the tail pipe.
It has a healthy spark on both sides, and it's obviously getting gas - otherwise it wouldn't be backfiring - but it won't run.

Any advice?

Thanks,
Allan

I copied this post from the blog area for Grognor.

Regards,
Russo

Jack · Full Member Joined: Mar 15, 2005 Posts: 411

Russco........I wish my R/90 shot flames out the old pipes Mr. Green

Did you do a complete build up ? But it does sound like the cam timing maybe off a tooth,which will give the symptoms your describing and what's happening is the exhaust valve is open during combustion thus shoots flames out the muffler tail end,which makes for a great night show though Rolling Eyes

Do you have my phone #? cuz I can swing over to lend a hand if you'd like...........Jack

Grognor · New Member Joined: Jun 03, 2005 Posts: 2

Thanks for the offer, but I live in Welland, Ontario. It might be a bit out of your way.
And thanks for moving my post to the appropriate place.
I was thinking it's probably a timing issue, but I haven't discovered the secret of adjusting the timing on the bike yet.

Allan

Jack · Full Member Joined: Mar 15, 2005 Posts: 411

Allen.......Well that blows my weekend adventure in the water Mr. Green

First check the point gaps and the static timing,adjust the valves to spec and the timing marks on the stator and generator,then rotate back to TDC,then check the valve clearances on the right cylinder and if the intake clearance is found to be tight,then most likely the cam timing is off,which means the motor needs to be removed for the next procedure>
Just bring the right piston on TDC,check the timing marks on the stator and the mark on the generator as they call it,they should line up perfectly,then check the timing on the camshaft sprocket,it should be facing on top and it needs to be centered looking down the sproket,bearing and camshaft. If not loosen the cam chain tensioner,remove upper rocker box to gain access to the chain,pull the cam end bearings and rotate the camshaft till the center Timing Mark lines up centered and reassemble. Make sure there's no slack in the chain towards the front cuz it needs to be tight there and the slacks towards the rear to adjust the chain slackness during running. Hope this helps you out.............Jack

Grognor · New Member Joined: Jun 03, 2005 Posts: 2

Thanks Jack,

I'll give it a try,
Allan

grizld1 · Posted: June 20, 2005, 3:06 pm Post subject: Re: Grognor's / balls of flame

Allan, there's an easier way to check cam timing. Your camshaft sprocket has only 34 teeth, which means that 1 tooth is a whole buncha degrees. In the 78 engine intakes should open at 36 btdc and exhausts at 68 BTDC; valves should close at 68 ATDC (intake) and 36 ATDC (exhaust). Just set your cam chain adjustor and tappets, watch the tappets, and read the valve action from them. Check the spec. with a simple plastic circular protractor, determining angle between the timing mark on the rotor and the TDC mark on the case. If the cam's in the wrong position, things will be WAY off; this doesn't have to be a precision reading! Good luck; hope you haven't pulled your engine and head cover for this.

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