no bottom end power

[barkbuster350r]

I just got finished rebuilding my 86 trx 250r which included new crank, new rod, new main bearings, newly resleeved 88 national ported cylinder bored .10 over, rechambered head, 37.3 keihen carb, v-force reeds, paul turner "race" pipe, fatboy 2 silencer, and K&N filter with no airbox lid. I was riding at the sand dunes and noticed no bottom end power which may be normal, I don't know. My gearing was 12/36 with 20" skate trak II's. If felt like my old banshee... I would be pulling a dune and lugging, so I would have to slip the clutch to get it in the powerband in 2nd gear. My jetting should be right on, I had it on a dynojet and it made 44 HP with a 170 main, cel needle middle clip, 55 pilot. It rips on top end but just no bottom. Any ideas? I have a paul turner torque pipe, I think it's called a type 5, sitting in the garage. I might try that later. Thanks!

[Hoppedrap]

Try different gearing on my old 250 I ran 12/39 20" haulers

[Jester]

its prolly the 36t rear sprocket.

[barkbuster350r]

Yea thanks guys I think you are right, my gearing may be a little tall. I put some 18" holeshots on it today and changed the front sprocket to a 14, and it seems to have power everywhere. I think that the 20" paddles may have sucked too much power. Next time I'm at the dunes I'll try a 12/38 or 13/38.
Thanks again, Brad

[beerock]

you need a larger carb,

cr250 reed cage or cr250 radvalve 96-98

a diff pipe those paul turners are ehh.

try out a esr trx 5 or if you can find one a curtis sparks tt or mx

my motor with 20" sand star paddles ran a 13/39 and pulled hard in every gear but i could not get 6th unless i was wot and slippin the clutch a bit


what kind of paddles are you running pics of the bike?

maybe you need a tire with less amount of paddles so you can get soem wheel spin. sound slike there hookin up to well.

[hollywood250r]

Originally posted by beerock
you need a larger carb,

cr250 reed cage or cr250 radvalve 96-98



A larger carb would lead to the loss of more bottom end. Sounds like gear is play a large factor in the low end power loss. Also, try the CEJ needle. The CEL can be a little lean in the low RPM range.

[beerock]

in dunes you need mid and top at least thats how i ride dunes.......

the larger carb has mroe gains then a small carb with bottom end. imho small carbs plug up the 250r motor. the cel works perfect with 265's if its lean you drop the clip/raise the needle

besides that why i said change the reed cage too. the cr250 reed cage and cr250 radvalve are the best and have crispness everywhere

the stock cage is more for mid to top while the radvalve is more all around and not as much top, but you can port them to fix that

[YFZRob]

The one area no one has addressed yet is your compression.

What's your static compression?? If it's 170 or less, you can make up quite a bit of low end just by bumping it a bit. Not sure if you have a CR or TRX head gasket, but if you are running a stock gasket, and your compression is 170 or less, jump to a CR head gasket. Higher compression will always boost bottom end.

[beerock]

rechambered head sounds like he has high comp maybe not.

good one though!;)

[YFZRob]

Yeah, I was thinking that too, but rechambered may not include any milling for compression. Who knows. Definitely need to know current compression though.

[barkbuster350r]

I have no idea what my compression is, I don't have a gauge that fits it. But the motor was just rebuilt and had only been broken in. I'm running a atc250r head gasket and 100 octane fuel half vpc12 and half pump gas and motul 800 mixed 32/1. I've been planning on getting a new compression gauge but haven't gotten around to it. Oh, and also, the guy who resleeved my cylinder included a piston kit. When I received the piston kit, it was a wiseco but not a pro-lite. I don't know if this makes much difference or not but I thought that a heavier piston would make more low end torque. Thanks!!

[barkbuster350r]

I'm running 20" sand skate II 8 paddle tires. I don't have a picture of it with the paddles on but here is a picture of my two R's. No problem with torque on my other bike.

[barkbuster350r]

a 2nd picture

[barkbuster350r]

I checked my compression today and with the motor cold, gas off, and throttle wide open it was 175psi.

[YFZRob]

Not bad, but there's definitely some more bottom end in your motor with more compression. You can try the CR250 gasket, which is a little thinner than the ATC gasket. It's probably only going to bump you to 180 or so, so it may not be worth it. You might want to get a Pro Design or ESR cool head with a 21cc dome with a CR head gasket. This will probably put you around 190-195, which will require more than pump gas, but not much more.....maybe 2 gallons of 110 to 3 gallons of 93. A 15 to 20 psi increase will really bring back your low end.

A while back on my 310 kit, I went from a pump gas to a race gas dome....all it did was take me up to 190 psi from around 170, but the soggy bottom end was cut in half. The typical 2 stroke soggy bottom was still there, but the motor came into power in half as much time as it did with the pump gas dome, effectively spreading out my powerband.

[250-R-250]

Wilkin would have to have a "powerband" around his nuts before he googled that:eek2: