[Joequad]

Hows it going, new to this forum im generally a Yamaha type guy, but I'm helping a buddy of mine fix his old fourtrax and cannot seem to get this thing to run. So I've already went through a couple of basic tests, compression test gave me 120psi at w.o.t. a spotless carb, disconnected the airbox, etc now for the interesting part, first I'm noticing the fuel pump isnt coming when I'm trying to crank it. I tested fuel pump and it works great, I am noticing it dosent kick on even to prime it when I drain the carb bowl.amd second I'm old school when i test for spark i just pop the spark plug out put it back in the coil and ground it to the engine.the weird thing is when I have it touching the engine no spark, but when i pull it off the engine so it's not making contact it will actually arc to the engine. I'm almost able to stretch the arc at least 1.5 inches but the second I make contact with the the cylinder boom no spark.ive never seen this before and not really sure what it means. I'm thinking to just try and hook up a on old gas tank and try to see if I can start it by gravity feeding the fuel for test purposes so I can eliminate one or the other from the equation.but any help would be greatly appreciated!

 

[shadetree]

you will find better help here ---> www.************ , its where all the smart atv mechs hang out now.

 

[Joequad]

you will find better help here ---> www.************ , its where all the smart atv mechs hang out now.

Nothing you can suggest?

 

[dclorty]

Nothing you can suggest?

CDI box OE# 30410-HA7-751

 

[Okie]

Take a old spark plug or your existing plug and set the gap at about 3/8 to 1/2 inch and check the spark. (darken the room when looking for spark across the gap.
If you have spark squirt little bit of gas into the carb throat or into the cylinder while the spark plug is removed and crank.. You need to download a SERVice manual for that rig, free from here. I found a printed version of the service manual on Flea bay awhile back for like $20
I'm headed for the new site that shadetree posted so as to check it out and register.

 

[Joequad]

Appreciate the help, I got it running, got him a new fuel pump relay and tried a new spark plug before I went with a new cdi, it had a brand new plug on there but I guess whatever one he bought the first was just, good ol' NGK never disappoints. It was however still really weird though. I have never seen a spark plug do that, in my experience they work or the dont but for some reason when it touched metal it lost all spark and then when it was pulled I guess the current from the coil was able to go straight through the plug to nearest ground i.e. the engine. Weird but uh well if it works it works lol thanks again

 

[Okie]

Yep, that type of spark was weird. I suspect the spark that could not be seen was maybe up around the top of the porcelain or so white it could not be see in light. I've bought those fuel pump relays from flea bay used with good results.
I've got a 87 fourtrax and when it would set at rest for few days it would crank for a long time before the fuel pump would prime and all electrical tests indicated all ok. Those fuel pumps do not get a full 12v from the relay when operating normally. I installed a manually operated momentary contact toggle switch on the right front fender and I can manually operate the fuel pump to prime the carb after the rig has been at rest for few days and it will start right up. The fuel pump has a pressure off switch internally and it will automatically turn itself off when it pressurizes. You can hear the pump running and when it shuts off. I posted then in a forum quite awhile back and couple other guys responded that they had sone the same.

Good to hear you got it going.

Them 87 Fourtrax 350 new and used parts are getting hard to find and expensive.

 

[Joequad]

That's not a bad idea, I was trying to just figured out a way I can rig up a top mounted tank so I can just delete the pump entirely and just run a petcock and gravity feed it like every other machine out there lol. But that's not a bad ide if saying the auto kill on the pump is working properly. I'll suggest it to him see what he wants to do. Again appreciate the help!

 

[Okie]

That's not a bad idea, I was trying to just figured out a way I can rig up a top mounted tank so I can just delete the pump entirely and just run a petcock and gravity feed it like every other machine out there lol. But that's not a bad ide if saying the auto kill on the pump is working properly. I'll suggest it to him see what he wants to do. Again appreciate the help!

The auto kill pump relay still works as intended when I added the manual prime switch to my 87 model. (the manual prime switch applies full 12v to the pump and when the switch is off the pump relay is re-connected) I used a Normally Closed, Single Pole, Double Throw
toggle switch. SPDT, normally closed momentary contact switch The switch has to be manually held in the prime position and when released the pump relay is re-connected normally. (the fuel pump relay on that Honda I think senses two things for safety, it senses if the machine is upside down the relay removes fuel pump voltage and also if the engine is not running no voltage is supplied to the pump. The pump is slower to operate when the engine is just cranking, therefore slower to prime when the the machine has been at rest for several hours/days/weeks, etc.
If my Yamaha with the gravity feed tank gets upside down with a rider trapped underneath the machine they might get gas soaked from the gas tank vented cap area and not a good thing being under a hot machine and gas soaked.

Those 1987 petcocks are expensive to replace also. If it ever quits contact goober. he has a recipe for using a $20 kit rebuilding.

 

[shadetree]

either you did the compression test wrong ?, or your gauge is not working right ?, these wont run very well if they are below 200 psi.

 

[Okie]

shadetree:
either you did the compression test wrong ?, or your gauge is not working right ?, these wont run very well if they are below 200 psi.

Good catch. With compression that low it should produce lots of blue oil smoke if the engine ever started up.

 

[Joequad]

200 psi? Really that much huh. Well now I'm second guessing my gauge, I did it full throttle and cranked it 5x and repeated the test a few times
The quad does smoke a little bit but nothing crazy, especially cause it was around 19° when I got it running so I wasnt too concerned

 

[shadetree]

200 psi? Really that much huh. Well now I'm second guessing my gauge, I did it full throttle and cranked it 5x and repeated the test a few times
The quad does smoke a little bit but nothing crazy, especially cause it was around 19° when I got it running so I wasnt too concerned

yeah, I don't have my service manual in front of me ?, but if my memory is half way good ?, I think it was around 240 psi ?.

 

[shadetree]

i looked it up from my manual , 178-206 is specs..sorry about that, I should have looked it up in my book .

 

[shadetree]

shadetree:
either you did the compression test wrong ?, or your gauge is not working right ?, these wont run very well if they are below 200 psi.

Good catch. With compression that low it should produce lots of blue oil smoke if the engine ever started up.

yeah, i had to correct myself, I quoted him 200, but 178 in min specs, 178-206 is best for a good running engine .

 

[shadetree]

200 psi? Really that much huh. Well now I'm second guessing my gauge, I did it full throttle and cranked it 5x and repeated the test a few times
The quad does smoke a little bit but nothing crazy, especially cause it was around 19° when I got it running so I wasnt too concerned

i hope your rings are just worn ?, if your cylinder is past current spec's ?, then you will need to have the cylinder bored over to next size up, rings, piston kit, depending on what size you have now ?, well..good luck getting all the parts !.

 

[shadetree]

cold or not ?, blue smoke is a sign of worn rings ?, or carb running rich ?. but if you did compression test right ?, then my money says your rings are worn.