Quad Bike

Selous

Well-Known Member
Would appreciate advice from those who know more than me regarding quad bikes.

I have just moved house and in to the bargain came a Yamaha Big Bear 350 4wd quad that I believe was probably made around 1990 or so. The bike is in decent nick considering its age and has done (according to the milometer) 4299km assuming it hasnt been round the clock already! There is little obvious corrosion and the plastics seem reasonably intact. Tyres have a good amount of tread on them.

Trouble is that although the engine will turn over on the button it will not fire, probably associated with a fuel leak that Kuwait would be proud of from around the in line fuel filter.

Has anyone any experience of this type of quad, my gut feeling is to get it looked at and assessed before deciding whether to keep it or move it on. What would you think it would be worth and have they been reasonably reliable.

Cheers

S
 
You need to drop the plug out. Get another new plug and earth that one to the engine block. Then turn it over and make sure you have a spark. If you dont try to disconnect the coil earth lead and check again. If you still don't have a spark then you could have a duff CDI unit/Coil/Pick up assy. If you do get a spark then check you have fuel in the float bowl of the carb. There should be a drain screw in there somewhere. Also check your compression.
They're no different from any other 4 stroke engine. Fuel+air+compression+ spark= bang. Make sure you have all the components
 
used to have one good racks can take 4 hinds no bother not as tough and reliable as the honda i changed it for if your useing the bike every day get rid of it and buy a honda but for recreational use there ok
 
I have the same as well, teyhan1 says it all...it's just an engine at the end of the day. The fuel filters are a quid or so from you local motor factors place and are very easy to replace. Also try some new fuel and a good dose of carb cleaner through it in case it's been sat with fuel in the bowl for while as it can leave deposits in the jets (blocking them).
 
Thanks for the replies, really helpful. petrol is self changing in that you fill it up and it ****es out the side!! so has no opportunity to block anything Cheers Andy, you busy over the weekend??
 
Thanks for the replies, really helpful. petrol is self changing in that you fill it up and it ****es out the side!! so has no opportunity to block anything Cheers Andy, you busy over the weekend??

sounds like you have a stuck float in that case. petrol left anytime is awful stuff can i just say the best way to find fault is do one thing at a time and easiest being first. like others have said plugs check for a spark no spark check the rest of the wiring.
cdi should be the last thing to go but it has been known for them to fcuk up. stator plate / pick up if this is faulty dont lob it as chances are its only the windings come loose from the plate and will re resin back and a cheaper way than buying new but back to the fuel i would take the carb off and undo the float bowl take out the main jets and pilot jets and blow them out with an air gun take the float bowl pin out and be carefull with the needle and blow everything out and put back together. atb wayne
 
An update for you kind lot who helped...
Fuel line replaced, checked spark plug which was absolutely brand spanking new. Earthed onto engine case and would get a spark intermittently. Found a dodgy joint behind the kill switch which was resoldered but this didn't help. Was having some issues with the key switch getting the ignition lights to come on. Eventually got it to fire and ran the engine for around 30 seconds. Now know that the exhaust is blowing and that there is an oil leak from the oil line to to oil cooler which we have subsequently patched as a temporary fix until a spare can be obtained.
The following day it was back to square one with no spark, a blown fuse ( was replaced) and lots of head scratching. Ultimately noticed that after a prolonged session of turning the engine over that the wires from the kill switch heated up. we stripped the outer covering back and found that the insulation had melted and was presumably causing a short across the kill switch circuit. After checking the wiring diagram we disconnected the kill switch wires from the dodgy ignition switch and the bike fired up immediately and has been running ok since then. Interestingly the kill switch still seems to stop the engine when it is running. Hopefully with a new ignition switch and oil pipe and a bit of a repair on the exhaust,we should be on the up from here.
A big thanks to all that helped and I hope you all have a happy and prosperous 2013
Cheers
S
 
used to have one good racks can take 4 hinds no bother not as tough and reliable as the honda i changed it for if your useing the bike every day get rid of it and buy a honda but for recreational use there ok

The army now use Yamaha in Afghanistan after swapping from Honda, they are tough bikes.
 
i had problems with a fuel leak like that and it was the float sticking and then the pin on the valve in the carb , easy to do yourself .
 
After checking the wiring diagram we disconnected the kill switch wires from the dodgy ignition switch and the bike fired up immediately and has been running ok since then.


Interestingly the kill switch still seems to stop the engine when it is running.

Then you haven't disconnected it have you.
Anyway glad it's now running, but if it was my money fixing it I would be looking at it all a bit harder.

Neil. :)
 
Totally agree with the above, although the quad is up and running the electrics remain a bit suspicious so I will keep looking.
 
The following day it was back to square one with no spark, a blown fuse ( was replaced) and lots of head scratching. Ultimately noticed that after a prolonged session of turning the engine over that the wires from the kill switch heated up. we stripped the outer covering back and found that the insulation had melted and was presumably causing a short across the kill switch circuit.

This must be a common problem, I have the Bruin 350 (same engine)... the key switch melted when the wiring loom rubbed through on the headstock. I had to cut out all the burnt bits and re-wire up to the keyswitch and replace the switch itself with a ride-on mower ignition barrel.
 
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