High RPM problem

[TenereStrider]

Hi everybody,

i bought XTZ 750 (1992) with a 40.000 km in a very good condition.
The bike was idle for couple of years in a garage in Germany.
We had carbs rebuild, put a new gas filter,new fuel pump,new oil,new oil and air filters,antifreeze,spark plugs,fuel pipe reparation.
Now the bike is working at like 900 rpm and when i drove it, i have a feeling that it has a problem of going to higher revs.
She gets rather quick to 4000 rpms and then the problem occurs altough i didnt have a chance to put her on a higway with a fresh tank of gas.
Does anyone had simillar problem?
Thanks in advance.
Greetings from Slovenia.

 

[Clawdog60]

Greetings
What’s the condition of the inside of the gas tank and petcock screen? Valve lash?

 

[TenereStrider]

The interior of gas tank is flaweless for what i see.
The petcock screen seems fine to.
The mechanic repaired the carbs and according to that i think that valve lashes are fine.
All of mentioned above is only my assumption because i am not a very good mechanic to be sure.

 

[Clawdog60]

Exhaust clean and clear?
Sounds like it’s starving for fuel.
I would think the carb float was set correctly

 

[Nikolajsen]

Ignition?
Not correct timing(don't know if it possible to set it wrong), bad coil?

 

[EricV]

Check simple things first. Is the throttle grip secure to the throttle tube? A slipping grip can make it seem like other problems.

Are the throttle cables working smoothly and lubricated?

Is the air cleaner free from any blockage? (I once had an open mesh air cleaner that had no issues until my pant leg would get sucked against it at higher speeds and block air flow.)

Will the engine rev freely when stopped and in neutral?

If so, do you experience the same issue in different gears?

If so, at the same rpm or at the same speed, or different?

If different, at what rpm and speed do you experience the problem for each gear?

Are the spark plug wires original or older? Any signs of arcing where they are against metal? Any cracks in the insulation?

Air, fuel, spark. Check everything for each category, doing each completely, before moving to the next category.

 

[TenereStrider]

I put fresh gas in the tank today. I have felling the the bike is working better. I will ride it on highway for the weekend. I hope she just needs a good ride.

 

[TenereStrider]

Check simple things first. Is the throttle grip secure to the throttle tube? A slipping grip can make it seem like other problems.

Are the throttle cables working smoothly and lubricated?

Is the air cleaner free from any blockage? (I once had an open mesh air cleaner that had no issues until my pant leg would get sucked against it at higher speeds and block air flow.)

Will the engine rev freely when stopped and in neutral?

If so, do you experience the same issue in different gears?

If so, at the same rpm or at the same speed, or different?

If different, at what rpm and speed do you experience the problem for each gear?

Are the spark plug wires original or older? Any signs of arcing where they are against metal? Any cracks in the insulation?

Air, fuel, spark. Check everything for each category, doing each completely, before moving to the next category.

Engine is reving but i feel that need to rev a little bit quicker.

The bikes runs good but i feel that is not good enough, like something is suffocate her.

When i close the throttle its seems that for second or two, the bike continues to accelerate.

Thanks for the advice. I will get myself to work.

 

[Jlq1969]

When i close the throttle its seems that for second or two, the bike continues to accelerate.

Spring of throttle/carb?

“Engine is reving but i feel that need to rev a little bit quicker.”

Full throttle tube/grip = Full open throttle body/carb???

 

[Clawdog60]

Vacuum leak?
Did that bike come with the “safety “ vacuum operated petcock? Worth checking over.

 

[HappyHiker]

If the carb has a diaphram, check for holes, leaks, tears and proper seal (especially if it was disassembled/reassembled for cleaning).

 

[Mak10]

If the carb has a diaphram, check for holes, leaks, tears and proper seal (especially if it was disassembled/reassembled for cleaning).

This. Especially if I the bike has been sitting for some time. The rubber diaphragm cracks and leaks and the bike will run but have low power. On Honda’s with multiple carbs it can get spendy quickly.

 

[TenereStrider]

Hi guys,
thanks for all the suggestions.
I will look it up and get back to you.