WELSH FLAT TRACK REVIVAL

[Adamc]

GONZO GONE POP! Or has it...?

The post below was in the Just Ride thread following my initial GONZO install:

So following @Jim advice I sourced another two Chineesium GN250 Igniter boxes from a different fleBay seller.
Today they came so I removed the first Gonzo box and replaced it with a new one.
Taffy fired up first press as usual. Ran fine on choke to warm; then knock off the choke and bike is on idle without complaint.
Apply a little throttle and POP BANG POP, B-A-C-K-F-I-R-E...... on the left cylinder.
Let it drop to idle and took off the UNI-POD filters.
Looking in the left carb inlet; apply a little throttle and POP - BANG again with flames coming out of the carb.... Impressive!

I'm wondering if an inlet valve isn't closing fully when the sparks arrive; causing back fire / flame through the carb?

Another valve check looms next week.

Any useful comments are welcome.

Ads,

 

[Jim]

GONZO GONE POP! Or has it...?

The post below was in the Just Ride thread following my initial GONZO install:
View attachment 251092

So following @Jim advice I sourced another two Chineesium GN250 Igniter boxes from a different fleBay seller.
Today they came so I removed the first Gonzo box and replaced it with a new one.
Taffy fired up first press as usual. Ran fine on choke to warm; then knock off the choke and bike is on idle without complaint.
Apply a little throttle and POP BANG POP, B-A-C-K-F-I-R-E...... on the left cylinder.
Let it drop to idle and took off the UNI-POD filters.
Looking in the left carb inlet; apply a little throttle and POP - BANG again with flames coming out of the carb.... Impressive!

I'm wondering if an inlet valve isn't closing fully when the sparks arrive; causing back fire / flame through the carb?

Another valve check looms next week.

Any useful comments are welcome.

Ads,

I'd suspect that carb Adam... most likely the pilot circuit has some blockage. Or possibly the float not allowing enough fuel in the bowl. If it was ignition (the GN box) it would most like cause misfires on both sides.

 

[Jim]

.... and if it was the intake valve, it probably wouldn't start and idle OK as you state.

 

[Adamc]

.... and if it was the intake valve, it probably wouldn't start and idle OK as you state.

OK, cheers for the pointers Jim.
carbs off again first.
Report soon.
Ads.

 

[jpdevol]

I've had synchronization cause such symptoms too - maybe try that first?

 

[Adamc]

I've had synchronization cause such symptoms too - maybe try that first?

OK, will do JP.

 

[Adamc]

FROM BAD TO WORSE......

Hello again.

This week I have removed the carbs cleaned and reinstalled them three times in as many days!
I can now get the carbs off and on without removing anything out of the way! Its easy once you work it out.

Today I just refitted them; filled the float bowels and fired her up. Right side runs fine but now the left side is totally dead. Checked for spark and it strong and regular on both sides. Timing seems good; cam chain tension is also good.

I have used the forum 'Carb Guide' as my reference bench mark.

Opened up left carb which is clean.
Shone a light though various orifices to see whats what.

Images below show main carb body. Pilot bung in place and removed:

Light shone through orifice

View through butterflies

Veiw of jets in situ, floats removed:

Jet removed with clean filter screen

Pilot jets clear (with side holes on shaft?)

Image shows carb cleaner sprayed through pilot jet orifice

Air jet shown / mix screw shown:

Views of carb orifices

These little holes are hard to know if they are clear?
Only the mix screw is a definite with soft copper wire poked through..
The other three are not easily accessible.

Mix screw showing in place. Then turned out three turns to match right carb.

Carb float height checked at 22mm at shoulder from gasket deck; matched to right carb.

Guys tell me what I am missing here?
I'm running out of logical explanations.

Cheers,
Ads.

 

[Adamc]

FROM BAD TO WORSE......

Hello again.

This week I have removed the carbs cleaned and reinstalled them three times in as many days!
I can now get the carbs off and on without removing anything out of the way! Its easy once you work it out.

Today I just refitted them; filled the float bowels and fired her up. Right side runs fine but now the left side is totally dead. Checked for spark and it strong and regular on both sides. Timing seems good; cam chain tension is also good.

I have used the forum 'Carb Guide' as my reference bench mark.

Opened up left carb which is clean.
Shone a light though various orifices to see whats what.

View attachment 251461 View attachment 251462

Images below show main carb body. Pilot bung in place and removed:

View attachment 251463 View attachment 251464


Light shone through orifice

View attachment 251465

View through butterflies

View attachment 251466 View attachment 251467

Veiw of jets in situ, floats removed:

View attachment 251468

Jet removed with clean filter screen

View attachment 251469

Pilot jets clear (with side holes on shaft?)

View attachment 251470

Image shows carb cleaner sprayed through pilot jet orifice

View attachment 251471


Air jet shown / mix screw shown:

View attachment 251472 View attachment 251473

Views of carb orifices

View attachment 251474 View attachment 251475

View attachment 251476 View attachment 251477

View attachment 251478 View attachment 251479

These little holes are hard to know if they are clear?
Only the mix screw is a definite with soft copper wire poked through..
The other three are not easily accessible.

Mix screw showing in place. Then turned out three turns to match right carb.

View attachment 251480

Carb float height checked at 22mm at shoulder from gasket deck; matched to right carb.

View attachment 251481 View attachment 251482

Guys tell me what I am missing here?
I'm running out of logical explanations.

Cheers,
Ads.

Anyone? @Jim @Mailman @jpdevol @5twins Help……

 

[Jim]

Anyone? @Jim @Mailman @jpdevol @5twins Help……

Unlikely, but have you checked one of the valves isn't stuck open or out of adjustment? Hold your thumb over the left plug hole and spin the motor. Enough compression there to blow your thumb off?

 

[Jim]

Also... just 'cause a plug fires outside the cylinder doesn't necessarily mean it'll fire under 150lbs of compression. I'd try a new plug just to eliminate it, if nothing else.

 

[Mailman]

Sure looks like you’ve done a good job getting the carbs clean. I didn’t add anything earlier because I honestly didn’t have any great ideas. I know how frustrating it can be chasing down a problem. I’ll just add to what Jim said, about the spark plugs, one time I had a cylinder not hitting and it turned out to be the spark plug wire, where it connects to the cap. It had a bad connection and the wires were burnt.
From here,
https://www.xs650.com/threads/1-cylinder-cuts-out.56920/#post-637310

Other intermittent ignition failures that had me pulling my hair out were, ignition coils that were breaking down ( but only when they got hot ) and I also had a Pamco electronic ignition unit that ran fine when the engine was cold but would begin failing as the motor got hot.

If you have eliminated the carburetors as your problem, that pretty much leaves you with spark and or compression. You just have to be methodical and start eliminating suspects. Don’t get discouraged, it can be frustrating and time consuming.

 

[Jim]

Also... the "Dark Ages" called... they want their vernier caliper back.

 

[Adamc]

Also... the "Dark Ages" called... they want their vernier caliper back.

Bloody hell boys, thanks for the responses. The vernier was my dads and it did him proud, and I’m no mechanic and it’s all I got.

New plugs were installed after the mis fire started.

Just found a float thread on here so will try a few solutions sugested there..

I‘m two years into this and still don’t have a reliable runner.

Onwards and onwards it will be.

Cheers
Ads.

 

[Adamc]

Unlikely, but have you checked one of the valves isn't stuck open or out of adjustment? Hold your thumb over the left plug hole and spin the motor. Enough compression there to blow your thumb off?

I suspected the valves from the start, but the wisdom of the forum sent me down another road. I’ll check tomorrow. Trouble shooting is nowt but trouble!
Cheers Jim.

 

[Kevin Werner]

Also... just 'cause a plug fires outside the cylinder doesn't necessarily mean it'll fire under 150lbs of compression. I'd try a new plug just to eliminate it, if nothing else.

The "Red Bike" ran perfectly last Monday. Wednesday it spit, popped, barked and sputtered in the lot at Tally Ho for the Smokies Rally. New (er) plugs solved the issues.

 

[Adamc]

The "Red Bike" ran perfectly last Monday. Wednesday it spit, popped, barked and sputtered in the lot at Tally Ho for the Smokies Rally. New (er) plugs solved the issues.

Cheers Kevin,
I just put new plugs and caps in. Could swap back to the old ones or buy another new set.

 

[Adamc]

JUST POSTING THIS TO KEEP A TRACK ON THINGS

 

[Team Junk]

Adam


Been away for awhile.
I would check your coil. Intermittent spark problems a lot of times are caused by breakdown of the varnish on the windings of the coil. A cheap Honda 750 coil repop would be a easy test.

Iechyd Da

Jack

 

[Jim]

Adam


Been away for awhile.
I would check your coil. Intermittent spark problems a lot of times are caused by breakdown of the varnish on the windings of the coil. A cheap Honda 750 coil repop would be a easy test.

Iechyd Da

Jack

Left side only, Jack.

 

[Team Junk]

Secondary is two separate windings "Me Thinks".