QuestionHi Chris, my son has a Yamaha TZR50 year 2000 bike which he bought second hand. The bike has run well for the last 6 months but now has developed a problem which I have been unable to fix. Bike has be been de-restricted before he owned it. I have checked basics are all working, spark plug, fuel filter, air filter, leaks and blocked exhaust with no success to pin down the fault. I have changed the spark plug which the bike came with NGK BR6ES to BR9ES recommended plug but experienced starting diffilculties from cold, so replaced the old plug and it starts fine. I stripped the carburettor to check all working, float etc but did not have manual to check if there were any correct height adjustment needed just checked operational.
Symptons: Bike looses power after running for short period, throttle response goes and will not pull. There is also smell of petrol indicating that the fuel is not being burnt in the combustion chamber.
Any ideas would be appreciated?
Br Gary
AnswerHi Gary.
This sounds like the bike is flooding out due to excess fuel.
Get the repair manual. It will have all of the adjustment specs on it. If you cannot find one at the local bike shop, then go to www.repairmanuals.com and order one there.
Pull the plug and check it for wetness/fouling. Check the spark gap as well. If it is wet, then the mixture is too rich. If it is fouled, it could be the same thing but not as bad. The fuel/oil mixture could be wrong as well. There are premixes that you can get for 2-stroke engines as well as premix devices that make sure that your fuel/oil mixture is always correct when you fill the tank. just to make sure, the mix is normally 50:1 fuel:oil.
The float could be working just fine, but what about the float seal? Is that in good sevicable condition?
There is also the possibility of mixture being off. Lean it out a bit at a time till it no longer fouls the plug.
Start with those and let me know what you find.
Good luck and ride safe.
FALCON
