11 replies to this topic

[africandutchman]

Hi,

 

I'm having a problem with my 1998 TDM850, because it stutters and does not want to rev up from low rpm.

 

As soon as it reaches 2500 rpm, it runs well and pulls hard, but low rpm is a problem. It sometimes has trouble starting, but after a struggle getting the revs up to 2500rpm, it sorts itself out. The fuel consumption is rather high as well. 8 to 9 litres per 100 km (I've even had as bad as 10), which is way higher than it used to be. used to get 5.8 to 6.5 litres per 100 km's. This started only recently.

 

When running the bike hard (for 5 km's or so) on the open road, it seems to sort the problem out. But then it starts again after a couple of stop-starts in the city.

 

I fitted an aftermarket exhaust, which made the bike pull strongly from low down and was way better than the stock unit. (and it sounds awesome)

 

Thought it might be an air leak on the carburettors, but after taking them off, found that there was no problem. Cleaned jets and cleaned out the carbs, but no joy.

 

The bike has done 64000 km's and looks very good for its age. Still running the stock jets. I live in Windhoek in Namibia, which is 5800 ft above mean sea level.

 

Can anyone direct me in the right direction, please?

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[adamwibberley]

Think it might need new emulsion tubes....

[africandutchman]

Thanks, Adam

 

I forgot to say that, when starting it cold and revving up for the first time, it emits a puff of black smoke from the exhaust.

 

I'll check out the emulsion tubes.

[Studley Ramrod]

Going off the symptoms you mention, in addition to checking the tubes, I'd check a few things out.

 

Check the coolant level and do an engine compression test.  The valve clearances might need adjusting.  Hard starting could mean the head gasket might be leaking.  Puff of black smoke could be worn or broked piston rings or valves need adjusting.

 

Check the carb fuel levels aren't too high.

Check the fuel pump isn't leaking fuel into the vacuum pipe that goes to the No1 cyl inlet stub.

 

Keep us posted on yer findings.

[chrisr]

That looks like a tough place to ride!!!

[TYREDNGRUMPEE]

Hi,

 

The bike has done 64000 km's and looks very good for its age. Still running the stock jets. I live in Windhoek in Namibia, which is 5800 ft above mean sea level.

 

Can anyone direct me in the right direction, please?

 

You have answered your own question, several times over.

 

You have aftermarket pipes, use loads of fuel and have thin air.

 

Every time I've changed silencers for throatier pipes the system has used more fuel. It won't help that you are 6000ft above sea level.

Emulsion tubes are the least of your worries but may need changing later.

I would experiment by dropping/extending the needles by a notch, so that you deliver less fuel for less oxygen.

 

Currently your system is gobbling masses of air by volume and chugging loads of fuel to go with it, but there's insufficient oxygen to burn the mix.

 

Understand, as I'm sure you do, that air is not the same as oxygen.

 

Black smoke = rich mix

 

There's your answer.

 

There's more than a few people here on this forum who will tell you that their Mk2 behaved differently and needed careful throttle control as it passed over the Pyrenees. I've just checked and the range of road altitudes are comparable.

 

There must be loads of workshops in the area that know exactly how to deal with this.

Edited by TYREDNGRUMPEE, 02 May 2013 - 11:14 pm.

[africandutchman]

That looks like a tough place to ride!!!

Hi Chris,

 

This is a country of wide open spaces.

 

1.8 million people in a country bigger than GB.

 

Lots of prime blacktop - delicious!

Going off the symptoms you mention, in addition to checking the tubes, I'd check a few things out.

 

Check the coolant level and do an engine compression test.  The valve clearances might need adjusting.  Hard starting could mean the head gasket might be leaking.  Puff of black smoke could be worn or broked piston rings or valves need adjusting.

 

Check the carb fuel levels aren't too high.

Check the fuel pump isn't leaking fuel into the vacuum pipe that goes to the No1 cyl inlet stub.

 

Keep us posted on yer findings.

Hi Studley,

 

The compression, coolant level and valves are fine. Those are the first things I checked.

 

The hard starting is only when warm or hot. Cold starts are half a second of starter and she fires.

 

Carb fuel levels, I'll check and also, I've fitted an electric pump and blanked off the vacuum stub into the No.1 cyl.

 

Will definitely keep you posted.

 

Thanks for your interest and comment.

[africandutchman]

You have answered your own question, several times over.

 

You have aftermarket pipes, use loads of fuel and have thin air.

 

Every time I've changed silencers for throatier pipes the system has used more fuel. It won't help that you are 6000ft above sea level.

Emulsion tubes are the least of your worries but may need changing later.

I would experiment by dropping/extending the needles by a notch, so that you deliver less fuel for less oxygen.

 

Currently your system is gobbling masses of air by volume and chugging loads of fuel to go with it, but there's insufficient oxygen to burn the mix.

 

Understand, as I'm sure you do, that air is not the same as oxygen.

 

Black smoke = rich mix

 

There's your answer.

 

There's more than a few people here on this forum who will tell you that their Mk2 behaved differently and needed careful throttle control as it passed over the Pyrenees. I've just checked and the range of road altitudes are comparable.

 

There must be loads of workshops in the area that know exactly how to deal with this.

Tyredandgrumpy,

 

Thank you kindly for your thoughts and direction.

 

I, sort of, needed confirmation of my line of thought, which I got from you. Thanks again.

 

When fitting free flow pipes, one usually has to rich the mix, but I thought that the mix would be ok, as it runs a little rich anyway. It transpires, however, that the mix, given the altitude, is way too rich anyway. (maybe I should have thought as much earlier, as we moved from a town which is 2000ft lower in altitude) I've had the pipes on for about 45000 km's now.

 

As I said in another post, cold starts are a breeze. Taken into account that the mix needs to be rich on a cold start, it follows logically that it would start easily.

 

The problem is getting increasingly worse, though. Which means that I would, as you suggested, drop the needles a notch, but also clean, at least, the emulsion tubes. And check fuel levels in the bowls. As the float mechanism is plastic, I'm not exactly sure how one would adjust them, but I'll check.

 

In Namibia, we are not exactly flush with bike garages and the work has to be done by me. All maintenance is done by me and I'm really finicky about it, as I love my bike and have a German background, which gives rise to a rather anal approach to these things. I mostly don't trust garages anyway, as they work for money and not love.

 

Thanks, once again, for your time and interest. It is greatly appreciated.

 

As a famous biker in our part of the world says: "Keep the rubber side down and hang on to those cables, Buddies!"

Edited by africandutchman, 03 May 2013 - 07:58 am.

[TYREDNGRUMPEE]

In Namibia, we are not exactly flush with bike garages and the work has to be done by me. All maintenance is done by me and I'm really finicky about it, as I love my bike and have a German background, which gives rise to a rather anal approach to these things. I mostly don't trust garages anyway, as they work for money and not love.

 

I suspect your spark plugs are currently taking a real hammering which is why things are getting worse. Listen out for detonation/pinking, use throttle control. You don't want to burn out a piston. If the needle operation improves things (I've never done this and am not sure if it's an available option, are there 3 positions?), then you may want to try returning the needles to their original position afterward and get some smaller jets for the bowl.

 

Someone here knows more about this than me. There are some mountain climbers amongst us. 

 

JBX?

 

Isn't there an aspect of the fuel delivery mechanism ie. idle jets that control a portion of the fuel delivery at idle and throughout the rev range afterwards?

 

I would use Google to find out what others have had to do at high altitude too.

Edited by TYREDNGRUMPEE, 03 May 2013 - 08:27 am.

[Studley Ramrod]

iirc the only parts that affect all rev ranges are the main jet size & the float height/fuel levels.

 

Yeah, the floats are plastic but they have a bendy metal tang for adjustment.

[africandutchman]

Just back from the test ride.

 

I took off the carbs, dismantled the both and cleaned jets and emulsion tubes. (not that I found much dirt or anything unusual)

 

Took out the slides and dropped the needles one notch. They were in the middle one of the three.

 

Assembled and tightened and set and....

 

I have now UNLEASHED THE BEAST!

 

By the initial amount of brown smoke, when revving hard, I take it a lot of carbon junk came loose. The smoking stopped before I got back home. (did about 15 km's)

 

Big smiles!

 

Thank you all very, very much for the assistance, guidance and support. Bravo!

 

Ride safe

[dablik]

Cool   there's some right clever bods on here......