Timing 180 deg out ?

[ukjules]

Help I have lost reason here.

I bought a wreck of a gsx 250 and it is going but seems painfully slow
and simply wont pick up speed as i remember it used too.

All tuning done in its current state:
Plugs, Carbs, Mixture, Valve clearances, normal air filter and air box.....

Looking at the timing again it tells me in the manual:

That TDC on number 1 cylinder (the RH cylinder as manual states !!) is when the T mark (on the R side of atu) is aligned
(see pic)

I thought number one cylinder was on the left as you sit on the bike ???

Anyway "if" I assume that the RH cylinder as you sit on the bike is number one then it is indeed at TDC
and the marks and cam chain marks all align correctly.
However later in the book it tells of valve clearance testing and again this doesnt makes
sense with discrepancies enfding up with checking the timing the book
simply saying to use the LH side ht lead for the timing gun.

Do you think my timing is 180 deg out ?

[John Park]

Maybe you've gained some weight since way back then. Seriously, your timing sounds fine and if it were 180 degrees out - which is impossible unless you swap the coil wiring - it wouldn't run.

If it gets to about 5k and then runs out of steam and burbles your advance mechanism could be stuck or tardy. They get rusty sometimes. If your exhaust system is clogged it would also do that.

Or your memories are rosier than the actual reality was. Those bikes should get to about 85 mph/130k with your face in the tach and your toes pointed out the back.

[ukjules]

I think you are right on "many" counts !
I for sure think my memories are rosier than the reality of today !

Update:
After almost losing the plot i discovered one plug cap was faulty, or at least had a very poor connection.
Unrelated i hear you say ....

Anyway I put on a new cap checked both and both had good sparks. The faulty one far better than before.
Put the cam cover back on without changing the cam chain position or the timing.

Putting the timing gun on the LH cylinder (which if you sit on it means the RH one - honestly with this manual)
suddenly the F mark was in view but not on the line and not possible to adjust to the line. Its slightly off.
So the timing is wrong and i dont seem to be able to have enough play to change it ?
Do you think the ATU is knackered ?

And also why it suddenly started to give correctish readings just by putting on a new working
spark plug cap i dont know - UNLESS when i put the timing gun on that one (the LH one if you sit on the bike
whjich i thought was origninally ...... oh lets leave it.

do ATU go bad ? as per one in my pic ?

GSX atu timing.jpg

[John Park]

It's hard to tell from that pic, but it looks like the spring is badly corroded. T is TDC, F is where it should fire at idle and R is where it fires when the advance is fully open which is usually just above 4,000 rpm. If the springs are hooped it may not stay closed, and if the mechanism is sticky you may not get it to respond at the right times - or at all.

I'd at least take the thing off and make sure it's doing its dance smoothly and snapping shut with authority. I doubt the springs are available separately, but the whole shebang is Probably the same as a GSX 400 part. I Think they both go from 20 degrees at idle to 40 advanced and are thus the same part, but you should check with cmsnl parts fiche before you buy anything.

That said, if it will advance to the R mark then the lack of power isn't due to that. And whether it is exactly at F doesn't matter as long as the fully advanced timing is correct.

This reminds me of a BSA 500 single I owned as my first bike [probably no faster than this 250 but a lot louder] that I lost the advance springs for. Too poor and stupid to just get replacements, I used two rubber bands, which worked great until the oil and fumes caused them to rot off. I'd know this had happened when it would attempt to launch me over the bars kicking it over.

[ukjules]

I tell you what there is no doubt that my memories are rosier than reality !
As I drive about on my GS550 below 700 revs usually trying to do that
on the GSAX 250 is not possible !

Like you said it is maximum revs and flat on the tank stuff.
It is however the best of trips down memory lane and ideal for small trips to the shops !

I have had the ATU off and it moves freely. It might have always but I cant be sure.
The bottom line is it goes like a dream but slowly !
I was expecting GS550 performance but it aint like that !

What fun though ! I recommend all get there old bikes back !