Board index Flathead Power-Technical Questions, Answers, and Suggestions 45 Flatties LINKERT M88 advice wanted

LINKERT M88 advice wanted

Post Fri Sep 17, 2010 7:58 am

Posts: 32
Hi - I have a 45, mildly tuned with no6 heads, high comp pistons, a little porting, mildly reground inlet cams, faster sprocket, and straight WR type pipe reaching to back axle.
I also have a M88 with 1 1/16 venturi, adjustable high speed needle.

I live in London, and I'm lusting after one of those funky little cast air cleaners, which has no filtration apart from keeping wildlife out.

Would you say this would harm my engine, and any suggestions about what I could do to dig out a bit more speed?

Post Fri Sep 17, 2010 9:03 am

Last edited by panic on Sun Nov 28, 2010 12:29 pm, edited 1 time in total.

Post Fri Sep 17, 2010 9:56 am

Posts: 32
Thanks for those tips.

The pistons are, I believe, slightly higher compression - maybe for a Servi-car? They're flat on top.
The engine was rebuilt by Fred Warr, who is the top guy for old Harleys in the UK. He fitted the pistons, and balanced the engine.

He advised me that the 1-1/8 venturi he fitted in there originally wasn't as effective as the 1-1/16.

I'm not quite sure what you mean by the shim on the fuel inlet?

So you reckon the panty hose filter is just no good? Anything else to make those pretty little cast air horns have some protective function?

Post Fri Sep 17, 2010 12:04 pm

Last edited by panic on Sun Nov 28, 2010 12:29 pm, edited 1 time in total.

Post Fri Sep 17, 2010 5:19 pm

Posts: 32
My mistake re high comp pistons - I misremembered, thinking they were slightly higher comp but I'll take your word there's no such thing.

And the venturis he had were all pretty loose in my carb bore - he's retired now - and that seemed best for an on-the-spot job.

So how would I shim out the gas nozzle?


Post Fri Sep 17, 2010 6:34 pm

Posts: 3160
Location: Central Illinois, USA

Your motor hop-ups are no problem for a Linkert.

But a loose-in-the-body venturi is, as it will defeat the main nozzle's "accellerator pump" effect.

I'm not certain what Panic means by a shim upon the nozzle, unless he means a seal around the spigot.
In which case, I encourage it as well!


Post Fri Sep 17, 2010 8:53 pm

Last edited by panic on Sun Nov 28, 2010 12:29 pm, edited 1 time in total.

Post Sat Sep 18, 2010 1:36 am

Posts: 32
I love this site - you guys are positively oracular!

I tried seven or eight new venturis, and the one I have was the best fit - tight to get in, but I can still see a very thin crescent of daylight at the bottom. These were all new, some original.
Best I could do, then, as I don't want to get a new carb body just yet.
The old venturi was really loose - rattled in the bore. Both needles were blunt - but the bike still ran well, even if hard to start sometimes.
I'm getting a new taper cut on the old high speed adjustable needle, as the old one was a custom-made bodge, a .35mm steel needle pressed then soldered into a 5/16 BSF allen-head screw. Either that or have a new standard needle pressed into a new screw.

So where do you think I might find a suitable nozzle washer, and how do I go about sealing the nozzle spigot? Bear in mind I live in London, and I'm not the greatest wrench. An electrical supplier? What size would that be?

Thanks guys.

Post Sat Sep 18, 2010 5:51 am

Posts: 3160
Location: Central Illinois, USA

I suggest swaging your venturis oversize on the outside diameter, and cutting them to a press-fit. The potmetal continues to shrink with time, and it will again be a slip-fit in a few years! Ideally, you could easily cut one from aluminum to a slip-fit as well. (Beware of commercial offerings that are copies of shrunken originals!)

Note also that you may be able to take a 1 1/4" Model venturi bore out to the neighborhood of 1.150".
That, and shaved shafts with soldered-in discs instead of screws, can increase your top cfm significantly.

For the shim/seal, I cut PEEK:

A thin wafer saves many venturies that have egged holes for the nozzle spigot.
A thicker seal that maybe more convenient for you is the phenolic gasket found in XA and 841 carbs, as well as K's:

JAMES Gaskets now offers them under the -52 part number.

I'm a little confused about the "5/16 BSF allen-head screw".
Were the original threads for the HS needle damaged that badly?
Or is that the same a 1/4"-40 NSF?

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Post Sat Sep 18, 2010 6:13 am

Posts: 32
Thanks for your reply.
I'll check out the gasket - I'm sure suppliers will be rubbing their hands in glee at the prospect of this transaction!

Regarding the needle seat, I'm puzzled too. Someone in the past has tapped out a new thread, prob 5/16 BSF, and made up a head to fit, then pressed a .35mm needle into that and soldered it.
Hard to see why, when factory originals would have done better.

Anyway, that's what they've done, and my worry is that the thicker needle has bottomed out in the jet and damaged it. The needle that's there looks kinda like the pencil in your pic.
What do you reckon I should do - go with the needle I have, or make a new needle with the original, thinner size?
And please don't say buy a new carb.

Post Sat Sep 18, 2010 6:53 am

Posts: 3160
Location: Central Illinois, USA

It is very common for the threads to be damaged on M88s because the original military needle set quite deep in the well, and a dull screwdriver would spread its slot and jam it.
For this reason, Larry Elias of the Netherlands produced needles with a knob that looks like the original cover plug, but also has vey long threads to reach down past the damaged area. They are also marketed through 45PartsDepot and others.

However, if your well has already been tapped oversize, you may be forced go with your plan; Just hope it aims at the seat!
For appearance, you could always drill out the center of the BSF screw to 1/4", lop off the hex, and silver-solder it to a civilian HS needle.

Got a lathe and a torch?


Post Sat Sep 18, 2010 8:35 am

Posts: 32
I've just heard from the old chap who rebuilt my motor - he was very pragmatic, saying as I'm not riding races or dispatches, and not a millionnaire, just get the old girl on the road to catch the end of the summer: don't worry about the venturi, it should be tight enough, and stick the old needle back in as it is.
He's sending me a jet to fit (take out the body plug), and suggests I screw the old needle right down. If the bike coughs a little when I snap it open, open the power needle up a fraction. See how it goes.
"There are no problems, only solutions" is what he says - can't argue.

Oh, and I don't have torches or lathes. Not even a shade tree!

Post Sat Sep 18, 2010 8:39 am

Last edited by panic on Sun Nov 28, 2010 12:30 pm, edited 1 time in total.

Post Sat Sep 18, 2010 12:53 pm

Posts: 32
Thanks for all the tips, guys.
Great help.

Post Fri Dec 23, 2011 11:53 am

Posts: 17
Location: POLAND
I have question. I do not want to start other post beacuse I need also advice. I bought Linkert M88, it's almost complete but it's very rusty. Of course body is OK but rest of parts look like would stay under water or underground for more than 50 years. I think some parts will be usefull but I need to disassemble it. I think I should put all the carb in any good penetrating fluid before I will start remove screws. What kind of fluid you can advice me. Now I'm thniking to soak the carb in diesel oil for several days. Maybe you have an idea what would be the best.

Post Fri Dec 23, 2011 1:31 pm

Posts: 6
PB Blaster is about the best thing ever invented for getting stuck bolts and such free. The problem might be getting it in your area. An electrc devce called a sonic cleaner is next on my list of things to buy, I've seen amazing results.

Post Fri Dec 23, 2011 9:27 pm

Posts: 2688
Location: Los Angeles, CA
into the wilderness carries about any Linkert replacement part you can think of.

Post Sat Dec 24, 2011 7:37 am

Posts: 3160
Location: Central Illinois, USA
Chris Haynes wrote:
into the wilderness carries about any Linkert replacement part you can think of.


I can think of some that are not listed.


Post Mon Dec 26, 2011 9:32 am

Posts: 17
Location: POLAND
Thanks, finding PB Blaster in Poland will be hard, I think impossible. I will try to find any replacement.
Replacement parts for Linkert is not a problem in Poland. We have here a lot of aftermarket parts for WLA in very, very good quality and reasonable prices. A lot of WLAs were in East Europe during war so there is a lot of motorcycles, and new aftermarket parts.

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