Author Topic: 91 lt250r powerband (Read 2342 times)

Jsmitty42 · « **on:** December 15, 2013, 02:17:18 pm »

ok so i got this quad not to long ago put a new piston and rings in it broke it in properly and when i went for a hard ride i noticed there is no powerband anyone know why this is or what i can do to make it hit hard ? its bored .80 over and has a fmf slip on

Iceracer · « **Reply #1 on:** December 15, 2013, 02:30:42 pm »

A stock Lt has no hit its like riding an electric motor. Its time for a pipe and possibly a bigger carb. If you still are not where you want to be time to consider porting it.
What kinda riding you doing?

MotorGeek - Jerry Hall · « **Reply #2 on:** December 15, 2013, 02:33:16 pm »

The power band is shaped by the overall engine design and how the exhaust pipe works with ports, reeds, carb and ignition.

Contrary to internet folklore and campfire bull sessions, the bore size and muffler do not really have much influence on the amount of power a two stroke makes

LT250RWV · « **Reply #3 on:** December 15, 2013, 08:08:39 pm »

Is your powervavle is working.. Dont know if your asking if you have a problem or it doesnt lead up to exception.

Jsmitty42 · « **Reply #4 on:** December 16, 2013, 05:43:57 am »

not sure if powerband is working and its bored .80 over and i trail ride

GrkGuy · « **Reply #5 on:** December 16, 2013, 06:41:33 am »

look in the little sight glass window on the left side, hit the throttle and see if the linkage moves.
next step is to see if it is set right.

LT250RWV · « **Reply #6 on:** December 16, 2013, 12:58:26 pm »

I had the problem with the power vavle 3 times after rebuilds. First time clip was broke. Second time piston broke and a piece of it smashed around the powervavle. Which was a nightmare to fix. 3 rd time didnt have a piece right after replacing the oring and bearings on powervavle. If its not closing you will not have any power band.

Jsmitty42 · « **Reply #7 on:** December 16, 2013, 03:55:22 pm »

ok so i went out and started the fourwheeler and let it warm up and gave it some gas about half throttle and the powervalve did not move hardly at all a very little bit but not much

Zilla273 · « **Reply #8 on:** December 16, 2013, 05:34:45 pm »

Remove the window cover and move linkage by hand, u should be able to push linkage like half inch and it should return quickly, it should have vary little resistance when u push

Chuckie25 · « **Reply #9 on:** December 16, 2013, 06:21:39 pm »

Y'all must have some amazing eyes because i can never see mine move...

Rider414 · « **Reply #10 on:** December 16, 2013, 07:27:50 pm »

Chuckie -

Its very clear (visually) when the exhaust valve opens and closes. Are you sure yours is functioning?!!!

LT250RWV · « **Reply #11 on:** December 16, 2013, 07:53:46 pm »

Pretty easy to see. Get a flashligh out it will help

Christph7 · « **Reply #12 on:** December 16, 2013, 08:23:49 pm »

I just bought an 89 LT 250R in great, stock condition and you should definitely feel it when the powervalve kicks in. It is not a "hitless" engine. On mine it almost feels like a turbo. The engine is pulling hard and then suddenly it is pulling really hard and the rear wheels are breaking loose. Fun stuff. I've read posts on this website that diss Suzuki's powervalve but I have to think theirs is either broken, out of adjustment, or maybe they've made mods to the engine that make it less noticeable.

Chuckie25 · « **Reply #13 on:** December 16, 2013, 08:24:20 pm »

Quote from: Rider414 on December 16, 2013, 07:27:50 pm

Chuckie -

Its very clear (visually) when the exhaust valve opens and closes. Are you sure yours is functioning?!!!

110% positive,,, and if its not i dont think i want it to!!! If it aint then my motor should be around the 90hp mark with it working LOL

LT250RWV · « **Reply #14 on:** December 16, 2013, 10:01:59 pm »

Quote from: Christph7 on December 16, 2013, 08:23:49 pm

I just bought an 89 LT 250R in great, stock condition and you should definitely feel it when the powervalve kicks in. It is not a "hitless" engine. On mine it almost feels like a turbo. The engine is pulling hard and then suddenly it is pulling really hard and the rear wheels are breaking loose. Fun stuff. I've read posts on this website that diss Suzuki's powervalve but I have to think theirs is either broken, out of adjustment, or maybe they've made mods to the engine that make it less noticeable.

The powervalve is their to help the quad in the bottom end. The hit your talking about is when your quad is running on the pipe.

MotorGeek - Jerry Hall · « **Reply #15 on:** December 17, 2013, 08:07:20 am »

A properly working power valve makes the hit less noticeable. Like LT250RWV said...the hit is when the engine is "on the pipe". On a 250, the power valve helps the power in the 6000 to 7000 RPM range. The surge in power usually occurs in the 7000 to 7500 RPM range.

Christph7 · « **Reply #16 on:** December 18, 2013, 08:26:07 pm »

I'm not sure I understand. If the power valve actuates around 7000 rpm--which conforms to my experience--how is the hit not a function of the power valve? It seems I read elsewhere on this site that the Suzuki powervalve is different than others in that it is not a gate that essentially changes the exhaust port height, but it controls the effective "tune length" of the exhaust by opening and closing a passage to a camber in front of the engine. In other words, it relieves back pressure at high rpm. At high rpm the passage closes and the exhaust flows more easily and that is when and why you feel a hit. Isn't this why some drag racers block off the passage for a pure top end engine? Or, does the hit (due to it being "on the pipe") come 1000 rpm or so after the passage closes? I'm just seeking clarification.

Iceracer · « **Reply #17 on:** December 19, 2013, 07:12:03 am »

As I remember on a correctly set up STOCK 250, the engine is very smooth and does not rev really high(compared to a ported piped machine) . The power valve makes the engine think is has a shorter pipe once it closes. If it closes at the correct time. You engine will be very smooth and linear. If it closes at the wrong time or not at all, You will notice a snap, hit or lack of power in general. It will fall flat and not rev out.
Closing off the power valve is only ever a good idea for a pipe designed specifically for that or Drag racing when your leaving well above it closing rpm any way.
It is not the most accurate mechanism for RPM. But in good repair and properly set it function adquetaly and there is not a readily avalable !!electronic counterpart. Ive looked into this but not finding a great alternative so far.

A machine with a big hit while it may be fun to ride, is not that fast compared to a linear engine . In the end its all what you like and do.

Rider414 · « **Reply #18 on:** December 19, 2013, 10:30:39 am »

Quote from: Iceracer on December 19, 2013, 07:12:03 am

A machine with a big hit while it may be fun to ride, is not that fast compared to a linear engine . In the end its all what you like and do.

This -

Chuckie25 · « **Reply #19 on:** December 19, 2013, 11:10:25 am »

Quote from: Rider414 on December 19, 2013, 10:30:39 am

Quote from: Iceracer on December 19, 2013, 07:12:03 am
A machine with a big hit while it may be fun to ride, is not that fast compared to a linear engine . In the end its all what you like and do.
This -

Truer words have never been spoken.

LT500Kid · « **Reply #20 on:** December 19, 2013, 08:06:43 pm »

all i know is stay away from the red powerbands

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Author Topic: 91 lt250r powerband (Read 2342 times)

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