cvrt clutch and direction lever

[BRDM Driver]

I had an issue a couple of days ago after the run back from Tankfest. Engine was hot and when maneuvering to get back into the garage (a bit of fwd/rev), the gearbox started making a very loud rattly groaning noise. It sounded like something not meshing fully.

It only did this in forward and only at higher rpm above 1500-2000.

As we had another vehicle to collect, I shuffled her into the garage slowly and returned to check again today.

No problems found today on a quick road run.

I did notice the the idle speed was very high with the hot engine, probably well past 750rpm, maybe 900rpm. I guess this was engaging the clutch and maybe the fwd/rev dog clutch wasn't quite home?

Anyway, I have put the problem down to being hot and having idle set too high.

Today I set the throttle stop screw to give a warm engine idle of 650rpm. Any slower and the ignition light starts to flicker and the idle gets a little rough.

 

So to my question!

 

I noticed that the clutch drum was stationary when idling as expected. BUT if I move the direction lever to mid way (so not engaged at all) the clutch drum spins. Once this happens it becomes impossible to get the direction lever engaged as the dog clutches wont work while rotating.

I know CVRT's can sometimes be difficult when moving from fwd to rev and back sometimes and the only way to avoid grinding the dog clutch is to turn off and back on again.

So should the clutch spin up on idle if you're not quick enough moving from fwd to rev ? If not, why is it spinning? Idle still to high? EMER says 500-600 and I have measured it accurately at 610-648.

This may be a non-issue but it does explain why it's sometimes impossible to change from fwd to rev.

Clearly the drag of the gearbox is enough to stop it, even when in neutral, so it's not fully engaging.

 

Any ideas welcome!

 

Edited July 4, 2018 by BRDM Driver
typo

[terryb]

you'll notice that idle speed increases slightly when fwd/rev knob is halfway, as there's obviously less drag, as moving less mass around. If the clutch drum isnt driving anything, and as it rotates freely around a roller bearing that's attached to the driven part of the clutch, then eventually it will pick up speed.

Your idle is too high-get the tickover smoother first-here's how;

make sure in neutral, engine at operating temperature

turn idle screw down to lowest possible speed'

turn one of the mixture screws in or out to achieve the highest possible smooth idle (you may need to turn the idle speed down as you do this)

now for the other  mixture screw-again, turn the idle down to lowest idle speed possible, and repeat the above.

when done, set idle to 500 rpm

also;

lubricate the fwd/rev linkage

make sure gearbox oil level is correct. remove and make sure gearbox oil filter element is clean, and that the correct grade of oil is used.

terry 

[BRDM Driver]

3 hours ago, terryb said:

you'll notice that idle speed increases slightly when fwd/rev knob is halfway, as there's obviously less drag, as moving less mass around. If the clutch drum isnt driving anything, and as it rotates freely around a roller bearing that's attached to the driven part of the clutch, then eventually it will pick up speed.

Your idle is too high-get the tickover smoother first-here's how;

make sure in neutral, engine at operating temperature

turn idle screw down to lowest possible speed'

turn one of the mixture screws in or out to achieve the highest possible smooth idle (you may need to turn the idle speed down as you do this)

now for the other  mixture screw-again, turn the idle down to lowest idle speed possible, and repeat the above.

when done, set idle to 500 rpm

also;

lubricate the fwd/rev linkage

make sure gearbox oil level is correct. remove and make sure gearbox oil filter element is clean, and that the correct grade of oil is used.

terry 

Hi Terry,

 

Thanks for this info.

So to confirm, when you say idle screw, are we talking about the throttle stop screw ?(item 9 in the J60 EMER s572 fig36)

And when you say mixture screw, you are talking about slow running adjustment screw? (item 8 in the J60 EMER s572 fig37)

 

I'll give this a go tomorrow... I really should cut a panel out of the firewall to make carb fiddling easier....

[terryb]

idle speed screw is on the spindle of the carb by the firewall-follow the throttle link rod 

mixture screws are towards the front of the vehicle at the base of the carb-there are two