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JLG40F engine question

dbris

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Mar 27, 2010
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32
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Los Angeles
My JLG40F has a Wisconsin engine that has no ID tag. I believe that it's a VG4D or VH4D and it has a distributor, not a magneto. My question is, what's the timing supposed to be set to, and is it possible that someone has a scan of the engine manual? Thanks, Dave
 

OFF

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It's a VH4D. I should have lots of those manuals laying around at work. I'll scare one up for you monday. :D
 

dbris

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Mar 27, 2010
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Thanks again guys, a service manual would be just the ticket! :) By the way, I got to looking a little closer at that Hi Drive valve that has 2 coils, and it's the same dump and bang-bang that's on the bang-bang side except the BB only has one coil (just a bang I guess).:D Turning them both on at the same time seems to work although the engine is so out of tune that it doesn't like the extra load. So now that everything else is working it looks like it's time to tackle the engine. Dave
 

OFF

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Quickest way to tell the difference between a VG4D and a VH4D is by looking at the carburetor. VG4D has a sidedraft carb, VH4D is an updraft.

I'll be working on an E-copy of the VH4D manual, but please and make sure which engine you have. Just cause it 'should" have a VH4D doesn't always mean it does. :D
 

dbris

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It's a side draft carb so I guess it's a VG4D. It is an old JLG40F so I'm not surprised that it's a little different. Dave
 

OFF

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spec is 23* BTDC @ 2000 RPM

Now the hard part. Take the flywheel screen off. One of the vanes has an "X" marked on it. Paint that vane white or yellow. Standing in front of the enging looking straight on at the flywheel, on the edge of the fan housing at about 10:00 oclock there is a square mark. That is TDC. Hopefully your housing isn't rusty (most are). This mark is also the center line of the "V" of the cylinders.
3-7/16" down from that mark (towards 9:00 oclock) there is a round mark on edge of the housing. That's your 23 degree BTDC mark. Good luck. :)

And I'll get a copy of both manuals scanned in for "future" use. :D
 
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OFF

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Thanks OFF, I won't be out there until next weekend but I'll give it a look then.
Dave

You're very welcome. :D

Now, a real world proceedure for rusty old engines with no markings left.
Find TDC for #1 cylinder on the compression stroke. Mark one of the vanes, (what ever one is easy to get at around the hood of the JLG). Mark the shroud/fan housing beside your vane of choice. Measure CCW around the circle of the housing that 3-7/16" and mark that. Good to go.
 

wildhorse trnr

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Feb 13, 2010
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Texas
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You're very welcome. :D

Now, a real world proceedure for rusty old engines with no markings left.
Find TDC for #1 cylinder on the compression stroke. Mark one of the vanes, (what ever one is easy to get at around the hood of the JLG). Mark the shroud/fan housing beside your vane of choice. Measure CCW around the circle of the housing that 3-7/16" and mark that. Good to go.

Thanks for the real world info, I have come across a few that are so rusty or have fins actually broken(concrete pumps).
Do you happen to have a number or name for someone that can bring the old magnetos back to life??
I have 1 that I need repaired and I have never attempted to repair one.:usa
 

old743

New Member
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Apr 22, 2012
Messages
4
Location
CA
Hi all...new here. I have an old 743 Bobcat with a Wisconsin V461D I'm trying to rehab. Came across this thread and was wondering if someone could post or email me any manuals or info on the engine
 

old743

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Apr 22, 2012
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Location
CA
Thanks a ton, Mojo!! ...followed the link and downloaded the manuals. That should help a bunch. If you have additional info handy I'd much appreciate ANY tips or advice. I picked the 743 up from a friend of a friend who'd had it sittin around for quite a few years unused. Fortunately I got it pretty cheap, because it crapped out on me just after I'd finished digging the new foundation on a job. (lucky timing, sort of...although my client wasn't too happy about the hunk of heavy equip. broken down in his back yard) I need to dig into the hydro system and see if the main pump's putting out the correct pressure, but I figured as it's had issues starting and I know it's burning a bit of oil, I should make sure the engine is in the best shape I can get it and make sure it's putting out the most torque it's capable of. Currently it's running real weak... won't turn r/or/l well and can't even make it up a steep drive under it's own power. Bucket functions, but when the machine warms up it starts to struggle under load...I've got a lot of work ahead, but I'm stubborn and I'd rather not just scrap the old girl. That just seems like a waste of good steel.
Thanks again!
 

VoodooMojo

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Jan 18, 2012
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It sounds like compression is getting low. Give it a rebore, new pistons, rings and valves and she will be good for another 30 years!
 

old743

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Apr 22, 2012
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CA
Thanks for the advice! Sounds like a compression test is a good place to start...It'd be great if I could keep her running for another 30!
 

edf

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Jul 19, 2012
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3
Location
mt. carmel pa
im new to this group and dont really do forums but i need people who know what they are talking about to help me out. im trying to buy a jlg40f( im not sure how old but it is before 2000? i belive) anyway im buying it from somebody who hasnt run it in 2 years. the battery was dead so i charged it. then i tried to start it but the starter doesnt have enough power to move the flywheel. so im thinking the motor is seized up. no that big of a deal the vh4d motor is very easy to rebuild cause i helped my dad rebuild his. i need to know how to unlock the brakes on this machine so i can get the electric pump to move it to a tow dolly.
 

OFF

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Alberta, Canada
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Welcome :)
Try another battery in there before you give up on the engine. That battery may not have the power to crank the engine
no matter how long you charge it. Could be a bad starter also.
To unlock the brakes, there is a little cover with a bump in it right on the end of each hub. They are held on with two 1/4" bolts (7/16" wrench).
Take them off, turn them over so the bump is to the inside and you've released your brakes (disconnected your drive hubs)
 

willie59

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Dec 21, 2008
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Knoxville TN
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Agreed, try another battery first.

And be sure you chock the wheels before you disconnect drive at drive hubs. If it's on a grade, she can roll. ;)
 

edf

New Member
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Jul 19, 2012
Messages
3
Location
mt. carmel pa
alright i will be sure to try a new battery and to definitely chock the wheels haha. and thankyou for the brake help. im trying to start my own painting company and i found that it is faster to use a jlg then a ladder and alot safer. thanks again i will post pics of my new toy when it is acquired
 

edf

New Member
Joined
Jul 19, 2012
Messages
3
Location
mt. carmel pa
alright so i ran into another snag in the gears. over the last 2 weeks i have been putting marvel mystery oil into each of the cylinder heads via spark plug hole. so today was the day i got the first reaction from the machine. i had a pry bar in on one of the flywheel teeth(not the best place but i work with what i got) and finally got some wiggle room.my dad actually has a vg4d not the vh4d and he said that it should be as difficult as it is to move the flywheel but i fell like if it isnt difficult then i run the risk of a blown head gasket? with his motor he said he can turn it with his fingers but then that shows lack of compression am i right? i cut a hole into the back of the chasis so the nut that is on the end of the camshaft can be accessed with a 1 5/8" deep socket hopefully i can get more movement throughout the cylinders. Im basically really trying to avoid tearing the heads off of this machine because of not wanting to pour money into it. i know this thread was not very productive but i want professional opinions. so please help me out
 
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