Linkert M88 main jet

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Linkert M88 main jet

Post by Spider-Man » Mon Jan 02, 2017 7:49 am

Hi all,

After a little advise, I believe my Wla is suffering from fuel starvation.

The bike starts and runs well, after a a few miles of riding power drops off I roll to the side of the road, powers dropped and then the bike idles. Off I go again up around 50mph for a few miles then the same again, the faster I go the shorter the distance before the power dies, slower I go the less this happens. Air leaks resolved, fuel pipe replaced, even the M88 fully rebuilt....

I know the bike had a rebore, I think up to 90thou??. The main jet is a #52. And I have now ordered both 10% and 20% bigger jets to try.

My question is....is there a standard increase to jet size by rebore/piston size increase, equating to the larger the piston the more fuel req. I'm assuming so?.

Appreciate any help

Spider


Lib45
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Re: Linkert M88 main jet

Post by Lib45 » Mon Jan 02, 2017 8:31 am

A big motor with a small carb won't suffer from fuelstarvation..it's just being hold back in power.
I think you're suffering..well your bike is..from a vacuum drawn in the gastank.
Make sure your cap is venting..; does the bike behave the same with the gascap opened up?

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Re: Linkert M88 main jet

Post by Spider-Man » Mon Jan 02, 2017 8:39 am

Hello,

Yes I've tried the cap on and off, makes no difference

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Re: Linkert M88 main jet

Post by Lib45 » Mon Jan 02, 2017 10:55 am

Carb venting properly?

If you suspect overheating due to starvation...what color are the plugs?

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Re: Linkert M88 main jet

Post by chibobber » Mon Jan 02, 2017 5:07 pm

It has been awhile ,but is'nt the M88 a fixed high speed needle.If you try to adjust it it will die out like yours is.Crank it in and leave it alone if it is a fixed high speed needle.
Like I said,it has been awhile,maybe all wrong.
Good luck
Bob

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Re: Linkert M88 main jet

Post by Spider-Man » Thu Jan 05, 2017 6:54 pm

Lib45 wrote:Carb venting properly?

If you suspect overheating due to starvation...what color are the plugs?


Hi, thanks for the comment. I didn't mention overheating? Plugs are fine, burning well with minimal carbon deposit, pick up when accelerating is also good.

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Re: Linkert M88 main jet

Post by Spider-Man » Thu Jan 05, 2017 6:59 pm

Hi,
Thanks for your comments.

I have ordered two new jets, currently #52, #57 and #64 ( I think). Due to the rebore and the increased size of the piston and incurring problems, similar to the bowl running dry of accelerating. I'm not sure what else it could be.

Any other thoughts?

Thanks
Spider

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Re: Linkert M88 main jet

Post by Lib45 » Fri Jan 06, 2017 12:22 am

I still don't think it has anything to do with jetsizes...
If your bike is able to suck-dry the carbbowl, it must have a very poor mileage...even carb-V8's can't do that!
I would really pay attention to your fuelsupply; check blockages, ventilation, fuelfilter, tap...
Do you have an aftermarket fueltap-rod?
They sometimes have holes that don't line up properly, blocking/ restricting the fuelflow..

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Re: Linkert M88 main jet

Post by hbtcoveralls » Wed Jan 11, 2017 6:17 pm

I don't think it's fuel related at all

Surprisingly a condenser will behave exactly the same way

I fixed a similar issue on two different WWII motorcycles (WLA and A 741) and in both cases it was the condenser that was the problem

try replacing the condenser and see what happens, it's much easier than messing with your linkert

Tom Bowers

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Re: Linkert M88 main jet

Post by Spider-Man » Fri Jan 13, 2017 7:00 pm

Hello,
It's been converted to electronic ignition. Starts first kick every time.

I'm still moving towards fuel starvation. If it's not jet size related, as suggested already, fuel supply. The fuel tap (unscrew type on th top of the tank) which was a after market one could be the issue.

As confirmed already, fuel tap, fuel line, full rebuild by Linkert, air checked, electronic ignition added and all have been replaced.

The issue still exists, starts, runs, picks up fine, the faster you go the quicker the issue happens the bike seems to be sucking the carb bowl dry. Adjusting high speed needle or low speed just creates running problems, delay in pick up etc.

Run the bike at over 50, she dies pretty quickly, pull to the side of the road and she ignites again to a tick over, leaving it for a while then you have responsive throttle again. Travel again wind her up and same sequence. Riding around smaller roads ( not motorways) the issue doesn't exist as you are on and off the power. Of course here in Dubai it's mainly 6/7/8 lane highways.

Thanks for all your suggestion any more are welcome, will investigate sizing the fuel tap/cock

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Re: Linkert M88 main jet

Post by 454ever » Tue Jan 17, 2017 1:16 am

Hello Spiderman,

Did you check the float adjustment and the float travel ? If the float level is correctly adjusted and the float is not hampered
in it's travel, the next step will be to rule out the gas supply system.

To make sure that the gas supply system is not the cause of your problem, you may try this:
disable the gas supply system by connecting a vented gas filled plastic container (equipped with a hose and clamps)
directly to the float valve seat. You may carry the plastic container inside a rucksack.

If the problem is still not solved this way, I suggest to replace the electronic ignition for a set of breaker points and condenser.

Regards - 454ever
Borne tor ride - forced to repair.

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Re: Linkert M88 main jet

Post by Spider-Man » Wed Jan 18, 2017 2:34 am

Hi all,

An update...checked out the fuel cock and all seems fine, no blockages and the reserve works fine too.

I haven't changed any jet as I'm swaying towards electronic ignition but can't be sure! Each time the fault occurs, the first signs are lack of power and back firing. I rode the bike today, sat at 50mph fine, then power dies and try to roll on the throttle and bike starts to back fire. Back off the throttle and the bike goes back to a tick over...change down and then power is back. Start off again, after the first problem the fault does occur more regularly, every couple of kilometers

May change back to the points as suggested (up the thread) maybe the power or charge to the battery drops off which then alters the electronic ignition position.......

Again thanks for all of the suggestions and feedback

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Re: Linkert M88 main jet

Post by 454ever » Wed Jan 18, 2017 3:31 am

Back fire from the exhaust or from the carburetor ?

The electronic ignition; manual advanced, or auto-advanced ?

454ever
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Re: Linkert M88 main jet

Post by Spider-Man » Wed Jan 18, 2017 5:27 am

Hi 454ever
I'm appreciating your support!

The back firing is from the exhaust not carb but like I say the power has dropped off by then. The electronic ignition is a manually adjusted one from W&W. The bike is running perfectly before this happens

What you thinking??

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Re: Linkert M88 main jet

Post by 454ever » Wed Jan 18, 2017 6:40 am

Reading from your reports, it seems that your problem is related to temperature and/or the revs of the motor.
I don't suppose that the temperature will be a factor, because the motor is performing well after a restart.

The problem might be caused by a loose contact somewhere in the wiring system. More revs, means more vibration.
You may try what happens if you disconnect the hot wire of the ignition module from the coil and subsequently connect the
hot wire of the ignition module directly to the battery plus.

If this shows no results, you may assume that the ignition module is (partly) at fault.

454ever
Born to ride - forced to repair.


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