Author Topic: LMIV carbs and jets and tune and tears.  (Read 871 times)

Offline bentombed

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LMIV carbs and jets and tune and tears.
« on: March 11, 2019, 10:29:45 PM »

I have been working on the tuning and running of my 87 LMIV- when i got it a few months back it was still stock, it ran ok but lacked lower midrange bite.

 i have upgraded the pipes which made a massive difference and now i  have been playing with different carb settings to get the most out of the motor.  I havent done anything to the accelerator pumps, the plan is to shut them off.

for the tune I am aiming to use the guzzitech/ed milich recipe.
in the bike currently
 50/3 slides,
K4 needle - middle clip
265ab atomiser
128 main
65 pilot


it has not been working that well  - i discovered that the left side choke doesnt seal properly which i think is letting in extra air or fuel and messing it all up. no matter what i do it runs rich.

two questions

so, can i rebuild the lever and replace the oring or do i need to get a replacement?

and two - where have i gone wrong with my jetting and needle slide combo?

any help is greatly appreciated.  the bike goes well, i am at the end of my knowldege now. I know it can go better,



cheers
ben

Offline kfz

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Re: LMIV carbs and jets and tune and tears.
« Reply #1 on: March 12, 2019, 02:56:54 AM »
The carb rebuild kit doesnt include the choke seal, not even sure you can get the seal out.  What have you tried to seal the choke.

Its been years since i set up mine.  I will take the look at the settings. I think I have 130 mains in.

Have you done anything to the intake?

Kev


Offline kfz

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Re: LMIV carbs and jets and tune and tears.
« Reply #2 on: March 12, 2019, 03:00:23 AM »
Are you sure its slack in the midrange? The BV motor likes to rev more than my MV might give the impression its flat when its not.

Kev

Offline Old Jock

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Re: LMIV carbs and jets and tune and tears.
« Reply #3 on: March 12, 2019, 06:13:23 AM »
Can't help with the choke issue

Your set up is different from Ed's recommendations to me (mine a 1000 but Ed's recommendations covered both IV and 1000 as I recall)

Mine were different with pilot & slide position

Pilot I have in is a 68

Needle position on mine bottom clip

I don't really know what is optimum but I can say with Ed's setup, for which I am immensley grateful, the bike was like night and day over what was in it when I got it

Oh a few have reported that the mains might be a bit small but so far I'm happy

John

Online brider

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Re: LMIV carbs and jets and tune and tears.
« Reply #4 on: March 12, 2019, 08:05:51 AM »
Are you sure its slack in the midrange? The BV motor likes to rev more than my MV might give the impression its flat when its not.

Many experts here on the LM models and I am ignorant of whether jetting can boost midrange, but in my brief ownership last year of a LM IV, it was annoyingly flat in midrange, and scary fast past 5500 rpm to redline. I learned to ride it in the higher revs to take advantage of the fun that model is supposed to bring.
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Offline kfz

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Re: LMIV carbs and jets and tune and tears.
« Reply #5 on: March 12, 2019, 01:00:46 PM »
Are you sure the rest of the bike is sport on.  Ignition system?  Have you replaced the 30 year old advance springs and made sure the bob weights are moving free?

Valves all done and compression good?

Online Stevex

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Re: LMIV carbs and jets and tune and tears.
« Reply #6 on: March 12, 2019, 02:10:32 PM »
If your choke is letting by then replace the piston which has a rubber seal built into it at the bottom.
These seals get distorted and compressed quite easily.
The lowest part of #29 here, or #30:

http://www.thisoldtractor.com/dellorto_parts_diagram_for__phm_carburetors.html

 
« Last Edit: March 12, 2019, 02:13:41 PM by Stevex »
Steve
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Online Chuck in Indiana

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Re: LMIV carbs and jets and tune and tears.
« Reply #7 on: March 12, 2019, 07:49:47 PM »
You might be able to turn the rubbers over..<snapping suspenders>  :smiley: or just order new choke plungers from MG Cycle for less than 10 bucks apiece..
The Eldo I got running this winter didn't have any, and it (sort of)  :grin: ran. Maybe a little rich.. :shocked:
Chuck in (Elwood) Indiana/sometimes SoCal

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Offline notbent

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Re: LMIV carbs and jets and tune and tears.
« Reply #8 on: March 12, 2019, 08:54:29 PM »
What exhaust system are you running?
Stock airbox?
I tried the Ed recipe in my LM5 with new PHM40's and it didn't work at all.
Mine has airbox, stock exhaust with collector and Keihan mufflers.
The Guzziology recipe works great for me.
150 main
57 idle
60 starter
268 atomiser
K19 3rd clip
60/5 slide
Cheers, Andy

Offline lazlokovacs

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Re: LMIV carbs and jets and tune and tears.
« Reply #9 on: March 13, 2019, 09:06:50 AM »
I never got a definitive answer to whether ed's recipe should be run with or without the accel pumpers

obviously without the pumpers you'd need a bigger main jet if you enjoy twisting handfuls of throttle and feeling the bike kick up a bit

I can't remeber what jetting I have in mine but I'll happily dig it out and post it here

I did some rudimentary dyno runs to dial mine in a bit



« Last Edit: March 13, 2019, 09:08:19 AM by lazlokovacs »

Offline Bazil

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Re: LMIV carbs and jets and tune and tears.
« Reply #10 on: March 13, 2019, 06:41:31 PM »
My Mark IV has been running rich on the left side for a long time as well, and I haven't been able to find the problem. It's had a new carb kit, new choke plungers, the Ed Milch recipe, pumpers disconnected, new manifold rubbers - you name it. The right side has had the same attention lavished on it as well, but the RHS plug doesn't foul. It's running pod filters.

I had a Dyna sensor die a couple of weeks back, and recently installed heated grips which stopped working after ten minutes. Worked out that the controller shut it down because it didn't like the power supply it was getting, which leads me to  thinking it may not be a carbie issue but a charging / ignition issue ( but still dont know why only the LHS fouls plugs). Maybe timing is horribly wrong LHS ?

My next job, which I dont look forward to, is to go through the charging / ignition system from alternator to plugs to see if I find anything.

Any suggestions appreciated !

Bazil
1986 Lario ( long gone, still missed)
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Online Groover

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Re: LMIV carbs and jets and tune and tears.
« Reply #11 on: March 14, 2019, 02:20:11 PM »
I found this in my notes and literature stashed away:

---quote --------------------------------
The rich running comes from terrible stock jetting. Euro jetting is terrible as well.
I have a jetting recipe to fix these bikes.

K4 needle, bottom clip
128 mains
68 idle
50/3 slide
265 atomizers

The most important thing is the atomizer and needle combo.  Good luck.
Ed Milich

----end quote --------------------------------

Looks like you are close, I think only the needle clip location if not the same. I think however, you also need to take into consideration elevation. I believe Ed is at sea level, and if I remember right, you lean the mixture the higher you go.


« Last Edit: March 14, 2019, 02:20:38 PM by Groover »
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Offline bentombed

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Re: LMIV carbs and jets and tune and tears.
« Reply #12 on: March 14, 2019, 10:57:31 PM »
UPDATE

i got a new plunger for the left side carb and kaboom!  almost all better!  much faster, better pick up through the gears, still a bit iffy at traffic speed riding but much better overall. Also, as happens with 32 year old bikes the right side carb started playing up :(  oh well.

I moved the needle clip to the bottom position, and left the 65 pilot in place.  it is a still a teeny bit rich, as evidenced by the carbon build up on the pipes but i think that is the float bowl heights that i have not yet checked.

I will keep at it.  thanks heaps. really appreciated


Offline Furbo

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Re: LMIV carbs and jets and tune and tears.
« Reply #13 on: March 15, 2019, 08:14:30 AM »
Well,

we've no idea what your intake system is, or your exhaust, but on my own LM V (same engine) I ran a set up similar to  Eds and Guzziology,  K&N's, and most importantly a Bub Hyper system exhaust. Moving the cross over up nearer the heads REALLY fattened the midrange.
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Online Groover

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Re: LMIV carbs and jets and tune and tears.
« Reply #14 on: March 15, 2019, 08:46:48 AM »
Furbo, do you happen to know if there are header lile the one you mentioned (with the upper crossover) that will work with the factory pipe types?
1981 Moto Guzzi V1000G5
1987 Moto Guzzi LM1000SE, a
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Offline notbent

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Re: LMIV carbs and jets and tune and tears.
« Reply #15 on: March 16, 2019, 10:26:10 PM »
UPDATE

i got a new plunger for the left side carb and kaboom!  almost all better!  much faster, better pick up through the gears, still a bit iffy at traffic speed riding but much better overall. Also, as happens with 32 year old bikes the right side carb started playing up :(  oh well.

I moved the needle clip to the bottom position, and left the 65 pilot in place.  it is a still a teeny bit rich, as evidenced by the carbon build up on the pipes but i think that is the float bowl heights that i have not yet checked.

I will keep at it.  thanks heaps. really appreciated

Bump.

Are you running an airbox?

What upgraded pipes are you running?

I'd love a list of jet recipes for my LM V...


Offline Furbo

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Re: LMIV carbs and jets and tune and tears.
« Reply #16 on: March 17, 2019, 08:14:14 AM »
Furbo, do you happen to know if there are header lile the one you mentioned (with the upper crossover) that will work with the factory pipe types?

They're made by Mistral and available from MG cycle. http://www.mgcycle.com/index.php?main_page=product_info&cPath=26_108&products_id=4968
 
This is what the system looked like: https://theguzzidoctor.com/wp-content/uploads/2017/08/IMG_20170624_112349253_HDR.jpg

You may have good luck calling Harpers, heaven knows what they might have laying about.
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Offline bentombed

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Re: LMIV carbs and jets and tune and tears.
« Reply #17 on: March 17, 2019, 08:20:14 PM »
Bump.

Are you running an airbox?

What upgraded pipes are you running?

I'd love a list of jet recipes for my LM V...

HI ya

I'm running K&N filters and some Conti replica pipes. I found that changing the pipes made a massive improvement in both performance and sound.

the bike is currently set up like this and is super fun

128 main
K4 needle, bottom clip
50/3 slides
AB265 atomiser
65 pilot
Floats set at 21mm, up from the standard 18ish mm. An old Guzzirider told me to do this, so i did, and he was right.





Offline bentombed

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Re: LMIV carbs and jets and tune and tears.
« Reply #18 on: March 17, 2019, 08:21:30 PM »
Well,

we've no idea what your intake system is, or your exhaust, but on my own LM V (same engine) I ran a set up similar to  Eds and Guzziology,  K&N's, and most importantly a Bub Hyper system exhaust. Moving the cross over up nearer the heads REALLY fattened the midrange.

oops
i am running with K&N filters and a conti replica exhaust from Pipemasters australia.


Offline bentombed

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Re: LMIV carbs and jets and tune and tears.
« Reply #19 on: March 17, 2019, 08:24:31 PM »
My Mark IV has been running rich on the left side for a long time as well, and I haven't been able to find the problem. It's had a new carb kit, new choke plungers, the Ed Milch recipe, pumpers disconnected, new manifold rubbers - you name it. The right side has had the same attention lavished on it as well, but the RHS plug doesn't foul. It's running pod filters.

I had a Dyna sensor die a couple of weeks back, and recently installed heated grips which stopped working after ten minutes. Worked out that the controller shut it down because it didn't like the power supply it was getting, which leads me to  thinking it may not be a carbie issue but a charging / ignition issue ( but still dont know why only the LHS fouls plugs). Maybe timing is horribly wrong LHS ?

My next job, which I dont look forward to, is to go through the charging / ignition system from alternator to plugs to see if I find anything.

Any suggestions appreciated !

Bazil


Hey mate - check your float heights. Mine were way out. also check floats for pinhole cracks and all that.

Offline double.d

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Re: LMIV carbs and jets and tune and tears.
« Reply #20 on: March 19, 2019, 12:50:57 AM »
Hey Ben i had some problems with chokes some years ago and decided to remove them altogether. In our climate you don't need chokes.
1986 Le Mans IV Black Since New
2014 K1300 R Black German Starship.

Offline bentombed

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Re: LMIV carbs and jets and tune and tears.
« Reply #21 on: March 19, 2019, 01:31:41 AM »
Hey Ben i had some problems with chokes some years ago and decided to remove them altogether. In our climate you don't need chokes.

that is a good plan -  not even the coldest day in queensland needs chokes :)  how would i go about doing that?

Offline double.d

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Re: LMIV carbs and jets and tune and tears.
« Reply #22 on: March 20, 2019, 07:16:17 PM »
I just unscrewed the choke bodies?? from the carbs and used them as templates to fabricate 2 x 3mm aluminium plates and screwed these to the carbs. I think the RHS has a thick plastic spacer block so the existing screws will be to long. I found some replacement SS items that were the right length.
1986 Le Mans IV Black Since New
2014 K1300 R Black German Starship.

 


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