610 Bobcat / Wisconsin VH4D troubles

Got a problem with the engine not wanting to run, acts like the choke is on. Will idle but won't rev. Cough's black smoke out the exhaust. Put on a new fuel pump, new spark plugs, wires, cap, rotor, points and condenser. I rebuilt the zenith carb, not much to it, but still no change. I pulled the valve inspection plates and checked for a stuck valve, everything looks good s far as that goes. Took a compression test, all 4 cylinders were close to each other, maybe a little low on compression, but for it's age and the amount of abuse that it has endured over the years, it will have to do. Any one got any ideas? The wife won't let me shoot it!!

Assuming you've checked the air filter and intake for obstruction, and even possibly tried running it for a minute with the hose off the carb.... I would get a pair of those insulated spark plug wire pliers and try pulling the wires off one at a time while it's running, see if you have one or two dead cylinders, just for giggles. Is it at all possible you have two of the plug wires switched around? Ignition timing, coil, resistor if it has one... Does it have the heat shutdown tabs on the heads with a wire to them? Been thirty years since I worked on a 610, so... LOL

Do a leak down test. 90% you need a valve job

My 600 will do the same thing when the points or condenser go bad. I know you said you put new ones on, but maybe you got a bad set out of the box. Are the points gaped right?, if memory serves me its about .020 (but not exactly sure with out looking it up). That can cause that also. I had a flooding when running problem similar to this once, got a new fuel pump (electric) same thing. I found out in only needs about 2-3 psi fuel pressure, most parts store electric pumps are 6-8 psi, over pressuring the needle and seat flooding the engine. Make sure you have a low pressure pump if it's a electric pump. Good luck, these old girls can get frustrating at times but they can be bought and paid for what some guys pay in monthly payments.I'd be lost with out mine, hope you get her figured out.

Also maybe check that your float hasn't filled up with gas and "sunk" in the carb flooding the engine, just another idea.

mark18mwm said:

Also maybe check that your float hasn't filled up with gas and "sunk" in the carb flooding the engine, just another idea.

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Thanks for the response's guys. I did everything you all mentioned, checked and rechecked what I thought it could be. It just seems to be pointing back to the carb and not shuting down the fuel, like it's flooding the motor out. I'll try and reset the float, maybe it's to deep, letting fuel past the needle. Just frustrating when it was running good, not great, but good, and run it into a pill of gravel and it just starts crap'n out and hasn't run right since. I'm almost tempted to rent a machine to finish the job, but rent can be as much if not more than a new carb off the internet!

jimjim1954 said:

Thanks for the response's guys. I did everything you all mentioned, checked and rechecked what I thought it could be. It just seems to be pointing back to the carb and not shuting down the fuel, like it's flooding the motor out. I'll try and reset the float, maybe it's to deep, letting fuel past the needle. Just frustrating when it was running good, not great, but good, and run it into a pill of gravel and it just starts crap'n out and hasn't run right since. I'm almost tempted to rent a machine to finish the job, but rent can be as much if not more than a new carb off the internet!

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Oh I almost forgot to mention, I found where the wife hid my .44 Magnum!!

Don't shoot the dang thing, as much steel as they used in those old dogs, it'll just ricochet off and get you in the backside!

:duh

Check the mechanical spark advance in the dist down under the point plate, they do rust up and then your timing is way off.

did it, everything works, the springs are all hooked up, weights move free. Pulled the carb back off, looked on the internet for a new one, WOW! Cheapest I've found is $225 and it's in PA!
Thinking about pulling the heads and put in new gaskets, maybe help with the low compression, dunno. It has spark, maybe not real snappy, but it will zing your fingers when ya mess around........! Just at my wits end on this thing!

Have you checked the timing with a timing light? I believe it should be at 23 deg. The engine has to be running 2000 rpm or more to check timing , if not the advance in the dist is still retarded to make it start easier. here is a link to a repair manual for the vh4d, maybe you can find some thing here to help. http://www.wisconsinmotors.com:8080/wm/images/catalogs/wisconsin/VH4D_Repair.pdf
Good luck, i'm sure you will find it's something simple but frustrating. You say you run it into a pile of gravel and it acts up, maybe you have a bad connection on the ignition switch or a bad ign. wire and you are not getting all the power to the distributor all the time. The "bump " of going into the pile may be making some thing loose contact. Keep us informed, I like challenging problems..... when they are not mine, Ha-Ha.
P.S. with the cost of ammo now it might be cheaper to buy a brand new bobcat than waste a round on her with the 44 mag!!

It sure sounds like a timing or spark problem, to eliminate fuel pressure troubles try running a small container of gas up high enough for gravity feed. Try just turning the dist a little advanced by hand and see if it affects it at all. Plug gap can also do it or even a bad distributor cap. Look inside the cap for carbon tracks between the posts. The one I had was troublesome till I replaced the cap , points and condenser and coil and ran a can of sea foam or two through it. good luck.

One thing I recall about these old V4 Wisconsins is that some of them have a very odd firing order.

If you look at the cam in the distributor some have four nice even spaced lobes each 90º apart. others have them at different positions. I believe it is two close together with 45º between them then the third one is 90º from the second one then the fourth one is 135º and then 90º back to the first one. The end of the rotor that passes the wire terminal in the cap has a Tee shape to it to allow for the cap wire to be spaced evenly despite the uneven spacing of the lobes on the cam.

As you mentioned changing the cap and rotor it is possible you have a rotor for the four evenly spaced cam lobes. Not sure this would cause the problem you have but it is something to check that does not cost any more money.

Next thing I'd check is to be sure the floats in the carb are not fuel logged. Give them a shake and see if they sound like they have fuel in them. One trick used on old motorcycle carb floats is to put the floats in a freezer for several minutes then take them out and hold them under water in a bowl filled with warm water. If they are leaking as the air in them expands you will see small bubbles coming out of the holes.

I had the same problem with one of these. noticed the plugs would blacken up real fast. Someone had filled it up with diesel oil. I worked on that pig for about 60 hours before I figured it out. I also remember back then when the same type engine had two spark plug wires reversed, that also had the same symptoms. Keep at it you will fix it....

never had any luck rebuilding those carbs, they never seem to run right after they are done.
i'd replace the carb

:drinkup

Any updates? Did you get it figured out? Please tell us what the problem was when you get it fixed, always good to know what fixes other folks problems so I can lock it in my memory bank in case my old girl ever develops the same trouble.

did you ever figure out the problem?

change out the fuel. That may be the whole problem. If fuel is old or has a high water content running it on choke if ofter a sign of bad fuel.

Maybe somebody put diesel in her by mistake?

I have had off and on minor problems with my 610 since I bought it 12 years ago that can be the weirdest things. Sometimes it runs great. Other times not so good without changing anything. Last summer, it decided that it would only run on full choke, and ran similar to yours. I doubt this will help but here is what I did that ended up making it run better than when I bought it, and it is consistently running great. I ordered a petronix kit to replace the points, condenser and breaker plate. Easy to do job and I didn't have to adjust the timing at all. Then a new rotor, distributor cab, plugs and wires. Next, I put in a new needle and seat and adjusted the float. Also new carburetor bowl gasket and a new carburetor to intake gasket. By the way, I think the carb to intake gasket is really important to be sealed. I think my old gasket was bad and that's why she smoked and would only run with choke on full. I know you basically did all of this already, but the main point of my post is that it is probably something simple like float level and carb to intake gasket. Hopefully this helps someone