11 replies to this topic

[tomge]

Hello fellow TDM enthousiasts,

 

 

I hope you can help me identify the problem with 1995 75k km tdm.

He has developed a backfire through the carbs since a few weeks.
 

I had a similar problem about a year ago. Then it turned out to be a small coolant leak from the thermostat housing that dripped on the RH sparkplug lead. That caused backfires at low rpm.

 

Once the leak was fixed, the backfires went away.

 

Now they are back... in force...

 

I saw the coolant leak had returned and replaced the o-ring in the thermostat housing. Replacing it made me spill a bit of coolant on the egine.

 

As my fuel consumption was pretty high, I ordered a full carb rebuild kit from kedo. not only changed out the emulsion tubes and needles,but also all gaskets and jets.

 

After having reassembled carbs and cooling system, engine started up , but ran very bad. 

Diside it could be the spilled coolant, so cleaned the leads, plugs an engine from all coolant residue.

 

Ran much better. But as soon as I turned of the choke, rpm pick up became irratic.short burst of throtlle cause backfires through the carbs.

once above 3000rpm, the problem goes away.

 

Any idea's?

 

Could it be to lean on idle? 3turn out on the idle screw

My tdm is equipped with a devil single silencer.

 

But has run for over 8000km smooth over 2013

 

Rubbers between carbs and manifold are cracking, but the "spray test" shows no changes in rpm when spraying on them.

have ordered in new ones to be sure.

 

valve clearance...??

fuelpump?

airleaks???

 

Any help would be much appreciated

 

Thx

Tom

[dapleb]

 

So it reappeared when you made all the carb changes? What make of mulshions and needles did you use? 

 

Without the carb info I woulda suspected HT leads breaking down or coils. 

[tomge]

NO, it re-appeared before I redid the carbs

having  to strip the bike to change the seal for the thermostat housing gave me the ideal opportunity to re do the carbs

I'll have a look if I can change my leads and plugs and take it from there

 

thx for the tip

I'll report back on my progress

[TYREDNGRUMPEE]

.

Edited by TYREDNGRUMPEE, 09 February 2014 - 09:40 pm.

[Studley Ramrod]

Difficult to know for sure what the problem is, as Dappers says, could be leads or coil, or it could be the carbs need setting up.

 

It may be that the pilot screws need adjusting, along with a carb balance, and perhaps the fuel levels need adjustment also.

 

3 turns of the pilot screw are only a base setting and can vary by +/- 1 turn or more.

[tdm850rider]

Check for holes in the exhaust.

[tomge]

what has changed:

coil and leads have been changed, rubbers between carbs and engine have been changed

 

result: no change

 

as soon as the engine warms up a bit, the throttle response from stationary is very hessitant, resulting in vibrations and backfires when thottle is opened too fast

 

I'm sot sure what I can do now...

 

exhaust is ok too

 

when cold, running on chocke the problem is not present

as soon as the engine temp rises and chocke is turned off, the problems begin...

 

any other idea's I can try?

[Studley Ramrod]

Difficult to know for sure what the problem is, as Dappers says, could be leads or coil, or it could be the carbs need setting up.

 

It may be that the pilot screws need adjusting, along with a carb balance, and perhaps the fuel levels need adjustment also.

 

3 turns of the pilot screw are only a base setting and can vary by +/- 1 turn or more.

[tomge]

forgot mention  symptom:

 

problems became worse after not running for a fun weeks.

it took a few minutes of crancking before he fired up.

first figured time made the fuel in the carbs evaporate and needed to be refilled...

but now has trouble starting even after 2 days.

 

could this be because of a defective fuel pump? could the other symptoms be because of a faulty pump...??

thx

[Studley Ramrod]

Difficult to say for sure, I guess it might be the fuel pump although I'd be inclined to think that a faulty pump would make the engine run poorly at high revs, not the low revs you mention.  However, it has been known for a worn diaphragm in the pump to leak fuel into the vacuum pipe that runs to an inlet stub on No.1 cylinder.  This can flood the cylinder and cause initial rought running at low revs but usually clears up after the engine's been running a while.  It can also cause fuel to run past the piston rings and mix with the engine oil, soooo, might be worth smeling the engine oil to see if it smells of fuel.

 

If it's been stood for long periods then it could be some of the carb passageways/jets/pilot screws are gummed up.

[tomge]

Hi guys

 

after a visit to a club member who has a 4 gas tester and more knowledge than me  , he purring like kitten again.

synch was a little off, and mixture was waaaay off.

 

now that those issues are solved, no more backfiring and a big smile on my face!!

 

let the miles pass under my wheels again!!

 

thx guys

 

Tom

[Bobos]

  However, it has been known for a worn diaphragm in the pump to leak fuel into the vacuum pipe that runs to an inlet stub on No.1 cylinder.  This can flood the cylinder and cause initial rought running at low revs but usually clears up after the engine's been running a while.  It can also cause fuel to run past the piston rings and mix with the engine oil, soooo, might be worth smeling the engine oil to see if it smells of fuel.

Hmmm... that's almost exactly what my bike's been doing for the last few weeks (amongst other things; cam-chain or clutch basket rattle, another set of tyres, maybe needs the ignition re waterproofing again, floating discs not really floating or warped (AGAIN!) gonna be a busy weekend!) Time and mileage are possibly taking their toll on my eight fiddly now.