I was given a 1990 250 Trail Boss 2x4 2-cycle atv that had been sitting in the weather for who knows how many years. After a few beers my neighbor and I took the carb. apart and clean it real good, changed all the oils and were able to get it running. We had some fun ridding it around but there are a couple of things that we cannot figure out and so I need some help.

1. After ridding the atv for a little while then come to a stop, the engine keeps on riving up and you have to pump the throttle a couple of times to slow it down but then it starts riving up again. So it is hard to shift the gear into nutral. What do I need to do to resolve this issue?

2. I have bleed the brakes and they will hold for a few awhile. Then it will loose pressure again. Possible bad master cylinder? if so then question #3.

3. How do you take apart the brake master cylinder?

Ohterwise it has been great to ride!

 

Have same bike in garage... Sort of a project... Had same problem with mine... Check the battery charge, believe it or not. Once the battery lost its charge the bike would rev up to full throttle, but once I put a new battery in it that problem stopped... Then it sat for a few months and the battery was below 10 and the problem started again until I charged the battery...

 

i would never have thought of that withe the battery my 1998 400 sport is the opposite if eth battery is dead it will put load on teh engine and it will slow down if not stall because it is trying to make to much power.

 

check your crank seals and carb boot seal for air leaks..

 

Thanks for all the information. I would have never thought about the battery. Since the old battery held a charge for a couple of weeks. I did not purchase a new battery for the atv. I will check on the seals and get a new battery.

Any information on how to take the brake master cylinder apart? I would like to replaces all the seals inside it. It was full of crud when received the atv and I tried to clean it out as best I could. The price of a new or used master cylinder is a bit pricey.

Once again thanks!

 

also check the oil injshon system my xplorer was doing the same thing the oil line was leaking at the intake manifold

 

if you found crud in the master cylinder chances are the rest of the system also has crud in it, master cylinder is the highest part of the system crud will follow fluid to other components. may neeed to disassemble entire system to remove all crud.

 

Yeah the battery thing blew my mind... How I found the problem way back when... The battery needed jumped so I hook up my jump pack and it fired up, disconnect pack and it rev'ed up, connect pack and it idled down... Back and forth due to disbelief... Check the charge on the battery and it was around 8 once started it was around mid 12... Charged battery over night and it was up to 12+ everything was ok... But once the charge feel the revving was back. Put new battery in and it was gone for about 6 to 8 months until it sat a few weeks and the charge dropped... Since then if the bike is sitting I disconnect the battery... Havent seen problem in about a year....