Yamaha TRX850 Enthusiasts Forum

just bought a t-rex, its one of those bikes on my list to own, however being 10 years old its been buggered about with in places, the standard cans had been cut degutted and welded back on, and under the end caps have been attacked with an angle grinder, so i've fitted some removable baffles to shut it up a bit as its awful loud (but its still noisier than standard)

however at 6500rpm it goes suddenly very flat, and then picks up slowly again and does rev to the redline but it doesn't seem to be in any hurry, if you shut off here it feels like it lacking fuel, any idea's?

also the cdi has the near side block connector removed and there are 2 spade connectors attached to two of the prongs on the cdi that are earthed to the battery, any insight into this would be helpful

thanks andy

PS at work there is a complete top end including head with cams, rocker cover, valves, barrels and pistons that belongs to someone i know if anyone is interested in making an offer, thanks

is it a Japanese import or a UK bike?

sounds like it's running way rich.

andys350 wrote:also the cdi has the near side block connector removed and there are 2 spade connectors attached to two of the prongs on the cdi that are earthed to the battery, any insight into this would be helpful

It´s got the TPS mod done to it, why....don´t know. Usually makes it lumpy on low revs..
Maybe you got FCR´s on the bike without TPS??

Has the bike been stood for along time ??

Before looking for something sinister maybe its just crap fuel.

Mine was horrible till I drained the carbs, flushed out the tank and lines and put new fuel in.

not an import (red bike, silver frame and engine) plus it has a service book from carnell's stamped from day one, i'm running it every day, and i've took a bit of the baffle i fitted away to see if the problem got better, still hits a wall at 6500rpm its like it cuts out momentarily and then feels rough as it approaches the red line, think i'm going to reattach the tps connector tonight on the way home, definately running rich, there's carbon build up in the ends of the cans, bugger

there's always carbon build-up in the ends of the cans. it don't mean owt.

you might want to check the carb setup - jets and needles and the air filter.

andys350 wrote:not an import (red bike, silver frame and engine) plus it has a service book from carnell's stamped from day one, i'm running it every day, and i've took a bit of the baffle i fitted away to see if the problem got better, still hits a wall at 6500rpm its like it cuts out momentarily and then feels rough as it approaches the red line, think i'm going to reattach the tps connector tonight on the way home, definately running rich, there's carbon build up in the ends of the cans, bugger

Yes, it could be a previous owner messing with the TPS, but I have to say it really sounds to me like dirt or water in the carbs. Try draining and cleaning out the tank, fuel tap, hoses, and either disassemble or at least pull the float bowls off the carbs, clean thoroughly and reassemble with care. Bit of a PITA to do, but it sounds to me like a very likely cause, especially if it's a FSH bike and no-one has buggered about with the jetting. Doesn't sound like the dreaded emulsion tubes to me - mine certainly didn't have those symptoms. But dirt, rust or water can get in just through letting the bike stand long enough and/or wet cleaning. In case you haven't (though you probably have), check the air filter condition if you're using a K&N or similar reusable panel filter.

Might be starving for air. Clean the air filter first before pulling carbs apart.

andys350 wrote:not an import (red bike, silver frame and engine) plus it has a service book from carnell's stamped from day one, i'm running it every day, and i've took a bit of the baffle i fitted away to see if the problem got better, still hits a wall at 6500rpm its like it cuts out momentarily and then feels rough as it approaches the red line, think i'm going to reattach the tps connector tonight on the way home, definately running rich, there's carbon build up in the ends of the cans, bugger

Please let me (us) know of your findings as the problem sound about what i´m experience although mine is sluggish on 4-5th gear from ~4500-5000
...kinda jerks, never done it before and i think it happened around the time i got some system cleaner in the gas so crud in the carbs could be it...

idl1975 wrote:Yes, it could be a previous owner messing with the TPS, but I have to say it really sounds to me like dirt or water in the carbs. Try draining and cleaning out the tank, fuel tap, hoses, and either disassemble or at least pull the float bowls off the carbs, clean thoroughly and reassemble with care. Bit of a PITA to do, but it sounds to me like a very likely cause, especially if it's a FSH bike and no-one has buggered about with the jetting. Doesn't sound like the dreaded emulsion tubes to me - mine certainly didn't have those symptoms. But dirt, rust or water can get in just through letting the bike stand long enough and/or wet cleaning. In case you haven't (though you probably have), check the air filter condition if you're using a K&N or similar reusable panel filter.

it's a FSH bike...but it has the TPS mod? Begs further investigation methinks. Certainly not emulsion tubes from the symptoms described.

the tps mod has been reversed and things are much better, however the alloy baffle plates (i made) i removed at the same time and they let more exhaust pressure at the removeable screw in baffles, which went awol on the way home, just hope they're not stuck in someones radiator grill or windscreen at some traffic lights somewhere

put some FST in the fuel and emptied the float bowls as well, and its sorted, but i've had enough and i'm disheartened with it, so now its fixed, its going to a new keeper

andys350 wrote:the tps mod has been reversed and things are much better, however the alloy baffle plates (i made) i removed at the same time and they let more exhaust pressure at the removeable screw in baffles, which went awol on the way home, just hope they're not stuck in someones radiator grill or windscreen at some traffic lights somewhere

put some FST in the fuel and emptied the float bowls as well, and its sorted, but i've had enough and i'm disheartened with it, so now its fixed, its going to a new keeper

Well, that was quick!

NEXT!

Well, that was quick!

NEXT! [/quote]


LOl must be a Blue one then, apparently they go quicker