jlo440 seems to not want to run

[chris lewis]

hello everyone,

i just finished rebuilding my jlo440 and installed it back in the bigmax. i tried to start it but cannot get it running. if i spray ether im the carb, it will run...but even with fuel coming back to the carb, it jsut does not seem to want to run. the battery is dead so i am cha rging it now...just have been pull starting it...and pull starting it...and pull starting it.

the carb is a walbro wr as I recall. it h been completely rebuilt last year...all new diaphragms etc.
it does seem to be pumping fuel...but seems like there is air in the return line...is it sucking air?
i have all brand new intake gaskets and phenolic spa cers between the intake and the engine and new gasket betweenthe intake and carb.

where should i set the idle screw on the carb as a starting point?

thanks
chris

[jpswift1]

Chris, First off, how is the spark? Did you try putting new plugs in? I personally would get rid of the Walboro carb........those and Tillotson carbs are just way too unreliable and sensitive. I'd use a 32-34mm Mikuni roundslide instead. You can find them on ebay off old snowmobiles pretty cheap.

[Bazooo guy]

If it starts with ether than you have spark.
Did you set the timing when you assembled it.
Set the needles at 1 turn open till you get it running.
Make sure there are no leaks in the fuel line.
Air bubbles in the return line are normal till its running.
Spray a gas oil mix into the carb instead of ether.(if its a 2 stroke)
If you flood it pull the spark plug and dry it and crank it over without the plug in to clear the cylinder of fuel..
Dont use the choke if you spray gas or ether in the carb.
If you have good compression and spark at the right time and fuel it should
start.
Set the idle screw so it just starts to open the throttle plate.
Keep pulling ...

[chris lewis]

Hi Bazoo guy.

Yes, it will start on ether...and do not want to continue to do that..especially with a fresh engine. It is a 2 stroke.

There are two needles on it...an idle screw and I guess a high speed needle.

Another question>>>> out of the Stator plate there is a brown wire..it is a ground. It is inserted in the female plug. On the wiring harness from the ignition switch etc, there is NO brown wire in the male plug coming from the ignition switch, wiring harness etc.

Is there supposed to be a brown ground wire? Otherwise, how would one kill ignition and stop the engine?

I will look for a Mikuni 32-34.

Thanks
Chris

[chris lewis]

Regarding the Mikuni, since the Walbro is a diaphragm style pump, would I just put a vacuum powered pump (like on a B@S engine) inline? is that what others have done?

Thanks
Chris

[jpswift1]

Regarding the Mikuni, since the Walbro is a diaphragm style pump, would I just put a vacuum powered pump (like on a B@S engine) inline? is that what others have done?

Thanks
Chris

That's exactly what you would do. Something like this would do the job:

VINTAGE MIKUNI FUEL PUMP RACE KART SNOWMOBILE SINGLE 1CY McCULLOCH ROTAX BRIGGS | eBay

[Bazooo guy]

The brown wire is a ground from the stator. It should be grounded all the time.
The ignition switch connects the 2 black wires from the coils (in the off position) to kill the ignition.
You should pull the spark plugs and turn the engine over to prime the carb untill you see fuel flowing thru the return line.
Heres the walbro manual.

http://wem.walbro.com/distributors/servicemanuals/ServiceManual.pdf

[chris lewis]

Thanks for the info on the brown wire. I will need to jump that brown wire since the male plug did not have a receiving connector in it for the wire. That is a bear to get to while the engine is in....hmmm.

I did figure out that the plug was partially disconnected on the ignition switch...hence it would not kill ignition. I plugged it in and there is no spark when the key is in the off position.

There is fuel flowing into the filter on the carb (it has a plastic filter that screws onto the base of the carb. There is also some gas (with bubbles) making its way back out of the carb on the return line to the tank....so it is primed....just seems to not want to be pumping gas into the intake.

Thanks for the WLABRO carb manual! SWEET!

Chris

[Bazooo guy]

Do a compression test on the cylinders or cover the intake of the carb with you hand when its cranking and see if its sucking air.
I think that engine has reed valves that could possibly be leaking?
It should run without the brown wire connected.
You can run it without the plug to the switch.
The magneto and secondary coils produce the spark ..... the wires to the plug are for charging the battery or for lights and the kill switch.

[hydromike]

There are no reed valves on a JLO....

[Bazooo guy]

Thanks Mike so we dont need to worry about that.
Chris did you modify the exhaust system?
Pull the spark plugs again and see if they are soaked with fuel.

[chris lewis]

I will check compression however it has to be very good. I replaced the pistons with NOS Wiseco units from Richards and I had the cylinder checked out by our in house CMM guy. The cylinders were not noodled out and were still very much in tolerance for standard bore.

I did have a JLO 400 in it which I bought thinking I could run it until I got hte 440 done. It had the same symptoms....so the only parts that are the same are the intake and carb...so I am leaning towards the carb as the culprit.

If I go to a Mikuni carb, I guess I will need the adapter plate, an air filter, some way of hard mounting the carb (I think the adapters are rubber necks...correct?). It was mentioned that I need to change the angle of the carb as well....anyone know the exact angle that the carb would need to sit at?

Thanks
Chris

[hydromike]

From your very first post, if you can spray starting fluid into the carburetor and it fires and runs well (until it's out of ether), and with all the other properties you've described, the problem is more than likely rooted in the carburetor itself somewhere.

Some folks have gotten the Walbro and Tllotson diaphragm carbs to run very well, but at the end of the day a Mikuni is more suitable/tunable for this application. A float style Walbro is another option; they were stock equipment on many Cuyuna (JLO) powered Scorpion snowmobiles. I ran one on a racer for a while and had no problems with it. Float style Walbros have the fuel pump built into the top of the carb and have a float bowl with a butterfly style throttle plate rather than a round slide like a Mikuni VM series. A Walbro float-style and a Mikuni carburetor will need to be mounted level.

There are Mikuni VM32s that have the flange cast right into the carburetor (many Attex machines had these), VM32s that are rubber-boot mounted and most, if not all of the VM34s I've seen are rubber boot mounted.

EDIT:: Here's an ebay auction for a Walbro float-style carb. 1980 Scorpion Whip 440 Carb Walbro Carburator Cuyuna 80 Sting TK | eBay

If the link is dead, it's item number 110819218810. I ran this same carburetor on my 440 Cuyuna my D/stock Attex for a couple years, and it was great. I caught a bad case of Tinkeritis and threw the Mikuni on just to do it.... No noticeable difference in performance when I got the Mikuni tuned in well. Just an option...

Oh 'nother edit. Here's a picture of how that carburetor mounts to a 440. That's the fuel pump with the pulse line on the top of the carb. Butterfly style throttle and butterfly style choke.

[chris lewis]

Thanks for the great information. I am very new to this (I bought this on a whim after having wanted one ever since I was little) and really am at a loss on it.
I have to be honest...I really do not want to buy any more used up stuff. I have over 1800 in this thing and I still do not even know if it drives. I bought it with the engine locked up.. I rebuilt the carb and it seemed like it was all OK... I "wish" there was a simple retrofit that was cost effective.

I will do some more poking around tonight and see if I can squirrt bottle it and adjust the carb to get it running. I have spark, I have compression and it will fire on ether....so it MUST be the carb.

I will let you konw what I find out.

Thanks!
Chris

[hydromike]

I have over 1800 in this thing and I still do not even know if it drives. I bought it with the engine locked up.....Chris

Okay, how's this for cost effective?

I'll send you my old (float style) Walbro carb off my 440 if you want it. I don't *think* I have a spare manifold lying around though, and you may need it for your engine. What are the numbers on the tag on the bottom-rear (intake side) of the engine? Something along the lines of 2F440-6? Six head bolts on each cylinder or four? I admittedly don't know if the JLO is mounted level on your Max, or if it's tilted forward. If the engine is mounted level, we're in good shape, and there's at least one $10.00 manifold waiting for you on ebay.

Don't give up, Chris. We can get you fixed up cheaply one way or another. It's our specialty.

Mike