Running rich & temp lack of gears?

[L.A.B.]

I then topped it up with 400ml of Red Line Heavy Shockproof Gear Oil. The manual said 420ml but at 400ml it was already above the oil level screw.

Draining the gearbox won't remove every last drop of oil so if 400ml or just under brings it to the level screw when allowed to level out then so be it.

Does the oil disappear elsewhere?

Most will disappear into the main gearbox housing.

It doesn't appear to get thrown around inside the casing in any way either.

Not in the outer section of the gearbox but things will be different inside the actual gearbox case (below) where the majority of the oil disappears into:

Shall I remove the oil level screw & drain off the excess, or just leave it?

It doesn't sound like you drastically overfilled it but maybe better to drain the excess if the level doesn't settle.

 

[Pushed it n rode it]

Where did the original oil disappear too, a good few years ago mine blew it out of the final drive shaft. Breather hole blocked solid on the inspection cover , turned it into a gear pump. Ok so not a commando but same gearbox ISH. Only up the road in Southam and did a first winter rebuild of gearbox after 42 years of use. Need not have bothered but worries about the dreaded layshaft bearing. Over a 1000 miles so far. Hitchcock's at Chadwick End are good with Amal ? Not sure about Mikuni's.

 

[L.A.B.]

Stripped the outer cover off the gearbox to find next to no oil & what oil was left was milky, a slight bit of surface rust on the heads of the bolts & the ratchet spring was touching the gear selector pawl.

Does the oil disappear elsewhere?

OK, so you removed the outer cover and sorry to ask the obvious but did you actually drain the gearbox by removing the gearbox drain plug at the lower rear of the gearbox casing as you said previously: "Also had a peek into the gearbox inspection cover to see what I could see. Gearbox oil is below the drain level ........"

 

[Luke Turner]

Cheers all! Will keep an eye on the level & top it up or drain as necessary.

& L.A.B, sorry, I didn't make it clear, I drained the oil from the lower gearbox oil drain plug.

 

[Luke Turner]

Back to the VM36.. I fired her up & let her warm up then started backing out the mixture screw past 1 1/2 turns but didn't notice a change in how she ran. What does that suggest?

I'm current running a 290 main jet & a 35 pilot. Shall I try a 280 main jet & 40 pilot?

 

[acotrel]

That’s correct for a race bike that only ever accelerates through the mid range.
Road bikes can cruise for miles on a steady state partial throttle opening. If its lean at that throttle opening, you’ll have problems.

Nigel, I have been thinking about what you have said. I suggested getting the motor to cough, then raising the needles one notch. What you seem to be suggesting is to raise them two or even more notches. When I run on methanol at low comp, I use 6D Mikuni needles in 0.116 inch needle jets. With a commando on petrol, you would use a similar needle but in either a 0.106 or 0.107 inch needle jets. With petrol, getting it right is twice as critical as it is with methanol. If I raise my needles one notch from where they are now, there is a significant drop in performance. If you are one notch to high with petrol, the drop would be twice as bad. I doubt that if you did it my way, you would start burning pistons and valves from riding using part throttle. The step from the notch where the cough occurs, to the next notch is relatively very big with petrol.

 

[MichaelB]

Gearbox oil takes quite a while to level out. You have to give it 10 minutes or so before topping up to the final level.

I'm glad you got it sorted.

Back to the VM36.. I fired her up & let her warm up then started backing out the mixture screw past 1 1/2 turns but didn't notice a change in how she ran. What does that suggest?

I'm current running a 290 main jet & a 35 pilot. Shall I try a 280 main jet & 40 pilot?

What happens when you screw it in?
I still think there is something amiss with the enrichener/Choke.
What position do you have it in.
Run position is the lever up with the plunger down.
Choke/enrichener for cold start is lever down which raises the plunger. H

 

[Luke Turner]

I've checked & cleaned the plunger assembly, there didn't appear to be anything amiss but I gave it a thorough clean just in case.

Yep, I do just that, push the lever down to raise the plunger when starting from cold & then knock it off (lever is then level) when running & hot.

 

[MichaelB]

I've checked & cleaned the plunger assembly, there didn't appear to be anything amiss but I gave it a thorough clean just in case.

Yep, I do just that, push the lever down to raise the plunger when starting from cold & then knock it off (lever is then level) when running & hot.

Ok,

If there is no change with the air screw going in or out. something is wrong. Either the jetting is so far off the minute adjustment of the screw has no effect, or you have air blockage somewhere.

 

[Luke Turner]

I'll kick her over again tomorrrow night & see when & if she responds to the air mixture screw.

I'll set my phone up to record a video so you can see & hear how she goes.

 

[MichaelB]

Myself, I would be pulling the carb down, complete soak.
Verify the needle jet is correct. Set the needle in the middle groove.

Then, I would get a new 260 main, a new air jet, a gaggle of pilots from 35 down to 25. When jetting down or up, I like to go one too far then back.
Also, I only use factory jets. Pattern jets are inconsistent.

One more thing. How fresh is your gas?
It’s not your main problem, but does have an affect on fine tuning.


Added, when taking the carb down, I would look over the air jet real good, it may be plugged.
And, just because your pilot says 35, doesn’t necessarily mean it is, may have been drilled.

 

[Fast Eddie]

Nigel, I have been thinking about what you have said. I suggested getting the motor to cough, then raising the needles one notch. What you seem to be suggesting is to raise them two or even more notches. When I run on methanol at low comp, I use 6D Mikuni needles in 0.116 inch needle jets. With a commando on petrol, you would use a similar needle but in either a 0.106 or 0.107 inch needle jets. With petrol, getting it right is twice as critical as it is with methanol. If I raise my needles one notch from where they are now, there is a significant drop in performance. If you are one notch to high with petrol, the drop would be twice as bad. I doubt that if you did it my way, you would start burning pistons and valves from riding using part throttle. The step from the notch where the cough occurs, to the next notch is relatively very big with petrol.

AL, I’m not suggesting raising or lowering anything. Actually, I fully agree with you that the needle needs to be ‘just on the rich side of right’.

My only point was about engine damage. You can hole a piston / seize a motor on a road bike by cruising along on a steady throttle opening just as easily as you can a WOT on a race bike.

When cruising at 70-80 miles an hour with traffic to concentrate on, traffic noise, wind noise, etc it’s very easy to miss the warning signs!

 

[Luke Turner]

It was recently refurbished by Steve at Motocarb (the man for Mikuni parts in the UK, others will verify). I've since had it off countless times to strip it down & clean out various parts.

VM36
Main jet 290
Pilot jet 35
Jet needle P2 6DH3
Slide 2.5 cut around
Air jet No. 2

It's always ran with fresh fuel, never old/stale.

 

[MichaelB]

It was recently refurbished by Steve at Motocarb (the man for Mikuni parts in the UK, others will verify). I've since had it off countless times to strip it down & clean out various parts.

VM36
Main jet 290
Pilot jet 35
Jet needle P2 6DH3
Slide 2.5 cut around
Air jet No. 2

It's always ran with fresh fuel, never old/stale.

Have you talked to him?
It's apparent you have way to much fuel, or not enough air or both.

 

[MichaelB]

You also may send this guy an email.
decentcycles.com . Greg Fauth
Super nice guy and helpful.

I know he used to run a 36 Mik on his 850.
He swore by it.
Not sure what he's running now.
He used to be here alot as norbsa.

 

[acotrel]

Are there major differences between a VM Mikuni and a Mk2 Amal ?

 

[acotrel]

Nigel, to me riding a motorcycle down any main highway in traffic is silly stuff. It is too easy to become a statistic or get booked for speeding. The only guys I ever knew who burned pistons one fitted a mega without rejetting, the other fitted high comp. pistons without rejetting.

 

[baz]

Nigel, to me riding a motorcycle down any main highway in traffic is silly stuff. It is too easy to become a statistic or get booked for speeding. The only guys I ever knew who burned pistons one fitted a mega without rejetting, the other fitted high comp. pistons without rejetting.

Al you are not listening to what Nigel is saying!
It isn't just at full throttle IE main jet that you can hole a piston
I have done it myself on a t140e when the inlet rubber split

 

[Luke Turner]

You also may send this guy an email.
decentcycles.com . Greg Fauth
Super nice guy and helpful.

I know he used to run a 36 Mik on his 850.
He swore by it.
Not sure what he's running now.
He used to be here alot as norbsa.

Cheers for that! I've emailed him.

I'll ring Steve at Motocarb tomorrow after spending another night in the garage tonight & hopefully getting out for a ride.

I've also read that I've been leaving my enricher on for too long. I thought of the enricher as more of a choke so would wait till the engine was hot then knock it off but folk on this forum knock it off as soon as the bike fires up. Probably not helping with how rough she sounded when riding down the road away from mine.

 

[baz]

Yep turn the choke off asap