trx90 bogging and low on power

[Pappy]

i figured i may get a faster response in this section....


our 90 engine started developing a bog yesterday. air filter was cleaned, and i even drained the gas and put fresh in it just to be sure.

i at first thought maybe the clutches were starting to go, but it doesnt seem to slip and i ASSUME this type of clutch will allow the engine to rev a bit higher when it starts going out?


another thought, was that my boy is riding a gear higher then usual most of the time and it could possibly be just that fatc, but it seems to not be as snappy. after the above mentioned filter cleaning and new gas, it did seem to respond better.

any help thankful.

[300exOH]

Maybe a little dirt got in the carb?

[Pappy]

its possible, i will check that when it cools down.

i was think also it maybe time for a new spark plug?

[wilkin250r]

The "it just started running crappy" problems can be tricky. Basically, like any problem, they are a process of elimination.

First, you're on the right track. Eliminate all the easy problems. Clean filter, new spark plug, fresh gas.

Rebuild the carb, make sure your floats are working correctly. If the floats aren't working, and the carb bowl over-fills, it will richen your mixture.

Check the compression.

[Pappy]

i pulled the plug. the color looked great, but we didnt do a "chop".

we had it on the dyno so im pretty confident about the jetting etc.

anyway, the plug was nasty. it appears that maybe from running it rch before the dyno session, carbon built up heavily on the insulator. it has started cleaning itself, but im guessing problem 1 was the plug. i cleaned it and throttle response improved.

i have a new larger carb to be installed next week, im hoping that will give us a touch more power. after reinstalling the plug, the bike responded great. infact he was over shooting his doubles if thats any indication of the improvement:chinese:

[wilkin250r]

If the plug is fouling up, you might want to double-check some areas.

You might be a tad rich.

Lower compression could actually cause it, because you don't get good, complete combustion.

The spark plug could be too cold, not cleaning itself and burning off deposits. Get a hotter plug.