Exhaust Decoke ?

[Dickrod]

Can anyone recommend how to decoke exhausts on my T350 ?

I have had them rechromed so whatever mothod I choose should not harm the chrome.

I used Caustic Soda a long time ago, it was really toxic to use and did not get out much carbon anyway.

I have heard of people filling the exhausts with gas and setting them on fire but I don't like that idea much either as I think it would damage the chrome.

Is there a modern product available which is specifically for this job ?

[oldjapanesebikes]

I would have expected that the rechroming process would have de-coked them for you - or was this done a long time ago ? Assuming you've been using modern injector oils and the mixtures are set up properly I'd be surprised that you'd need to de-coke them. Do you have some more information on the 'why' part ?

[Dickrod]

Yes, that is the big question - why ?

Basically because I am clutching at straws as to what can be wrong.

This bike has been totally rebuilt and looks like new.
Rebuilt crank, clutch, NOS cylinders and pistons / rings and top end bearings etc:
Carbs cleaned and rejetted to stock sizes with Genuine Suzuki parts.
Pingel fuel petcock fitted, new points and condensors, coils etc:
NOS stock air filter.
Hard to think of what else it can be.

Bike runs bad no matter what we do to it.
Wil not idle, starts of very high then gradually drops until it stops, no amount of adjustment with carb settings will stop this.
Bike has very little power and wil not rev past 5,000 in anything other than 1st gear, not even in 2nd will it pull past 5,000.
I am only thinking of the exhausts being coked up because I can not think of anything else.
Yes, I would have thought the chroming process would clean out the carbob, but I am not sure it really does so that much. They only dip them in the acid very quickly I am told and I think it may leave carbon in there.

Any ideas ?

Thank you

Rodney.

[tz375]

Carbon in the pipes won't make much difference as long as the baffles are clean.

Fast idle dropping until it stalls could be:

Blocked exhaust runs for a few seconds until it can't breathe and then it chokes itself - check that you get reasonable pressure out of the mufflers, or pull the mufflers off and run a long flexible shaft through like a drain rod or electrician's fishing wire.

Air leaks around the carbs would be the normal answer - check that with a propane torch or spray around them with something like wd40.

Partially blocked fuel flow from the petcock to the float bowls - sounds unlikely with a Pingel but pull the carbs off and suspend them over a container and turn on the fuel tap and see how long the flow remains strong. Should be no change over a couple of minutes.

Fouling plugs is also possible. Starts up and runs OK until one plug and thenteh other foul because float level is too high or pilot jets are not teh size you think they are.

Not responding to idle adjustments suggests either fuel blockage or pilot jets blocked.

Inability to rev suggests either it's loading up with too much fuel or insufficient.

OR let's take the contrarian approach, it you are 100% sure it's carbs, it must be ignition.

Does it have a strong spark on time every time? One trick is to insert a cheap spark tester between the coil and the plug and run it to see if it's consistent. Repeat on side 2.

[Cliff]

What do the plugs look like after she's been run? Black, wet, oily, dry, tan colour, white??
Have you tried running without the pipes/mufflers?
Check for air leaks between the carbs. and engine, check fuel flow to the carbs., check and adjust float height and ignition timing.
Good luck!

[oldjapanesebikes]

All the stuff the other guys said plus: crack the fuel filler cap open - if the vent in the cap is plugged you'll see something similar to what you describe. I'd also check for hot wires after you've tried to run it - hot coils, hot harness, hot battery, hot ignition switch etc. Could have a wiring fault.

[parksie]

My two cents worth - I'd be looking around the enrichment area (choke)

[Dickrod]

All of those suggestions make sense and I have tried all of those already.
Not put much thought into the Fuel Cap being blocked though, I will try to run it without the cap and see how it goes.

I will keep you updated.

[diamondj]

All of those suggestions make sense and I have tried all of those already.
Not put much thought into the Fuel Cap being blocked though, I will try to run it without the cap and see how it goes.

I will keep you updated.

If the tank was coated during the restoration and they used the stock cap while coating then the vents could be blocked.

Jim

[jabcb]

A variation on one of tz375's suggestions...

Try an induction-triggered timing light to test the ignition system with the engine running. It is powered by the battery & uses a clamp that goes around a HT ignition wire.

Right cylinder on one of my bikes didn't run right. The exhaust pressure pulses were much less than other cylinders. With the plugs laying on the head, I got nice sparks when manually operating all three points. Used the timing light on each cylinder with the engine running. The sparks for the right cylinder weren't strong enough to trigger the timing light -- timing light worked fine on other cylinders.

If you don't have one of these timing lights then you probably know someone that does. Have mine from back it the day when car ignition systems had points.

[Zook-e]

You might try reverting back to the original petcock. The Suzuki two-stroke line a very sensitive to fuel delivery on a stock bike. Any changes I made to fuel delivery (i.e. Pingle or other non diaphragm petcock) caused major carb problems. A pingle or other non-diaphragm petcock will deliver too much fuel for stock carb settings and actually flood the carbs causing a rich mixture and foul the plugs. I have done many carb rebuilds for customers have problems in this fashion. I have instructed them to get a new original petcock after the carb rebuild to stock specs and problems were solved.


On my highly ported T500 (Daytona on a Shoestring) bike with chambers and airbox the carbs retained stock settings with a pingle petcock on circuit a Daytona wide open because of the increased fuel flow.

[jabcb]

Zook-e, what about the vacuum Pingel petcock? Are they any better?

Have a vacuum Pingel on my 73 GT250 + inline fuel filters & it runs fine. Do the inline filters make any difference?

[Zook-e]

In line filters are fine. Vacuum petcock is fine as well. Straight flow pingle or other straight flow have always had a profound effect on jetting.

[Suzukidave]

I dont know if this could even be done with the 350 carbs but one list guy that had similar problems found out he had put the carb slides in the wrong carb so they were put in backwards .

[Zook-e]

I dont know if this could even be done with the 350 carbs but one list guy that had similar problems found out he had put the carb slides in the wrong carb so they were put in backwards .

Yes, that is also a possibility. Seems that sometimes we or I think of the more difficult approach rather than the simple one.