atc 250r reed spacer or no?

[william16339]

hi, i am doing a full motor rebuild on my 85 atc 250r, i have a fatty pipe, fmf silencer, boyesen reeds, and a 38 mm carb...if i ad the reed spacer, ill gain tourque, but how much? and how much topend would i loose?

[RIDE-RED 250r]

Basically a little bit on both counts. Not huge but it does effect it. It's more of a piece of the larger picture. The Fatty pipe is more of a midrange pipe in my experience, at least the way my old engine was set up. It was a stock cylinder, 38mm PWK/AS carb, upgraded reeds with spacer, Fatty with FMF silencer with a high compression head gasket setup. That setup had a VERY meaty midrange, but I could feel the power fade away quickly when approaching top end. It was alot of fun to ride, but I like my curent big bore setup better. :naughty:

As far as exactly how much the spacer effects torque and top end power by the numbers, I really don't know. I'm sure when put on a dyno that results would vary depending on each particular setup method and state of tune.

The way you are set up I would probably run the spacer. You are set up almost exactly the way I was before the big bore and it ran pretty well.

Did you ever get your cylinder ported??

[william16339]

thanks alot man you help me all the time lol...no i did not i decided not to.......but with a full engine rebuild, 38 mm air striker, fatty and boysen reeds, i know i will gain bottom, but would i loose top or would it be the same? because power reeds are more for bottom-mid, my pipe is mid, but the carb i am putting on it is more topend...so with the carb im gaining topend but with the spacer im gaining lowend, so would it be more top less low, more low less top, or more low more top overall? lol

[rjs89ia]

your not going to gain or lose enough of either to notice unless you have a dyno. little things like spacers only change the equation by very small numbers. when i ran the spacer i didnt notice much of a difference about the only thing i did notice is how much clearance you dont have between the carb, gas tank, and frame its pretty tight fit.

[william16339]

i see, well i wanted tourque for trails, but i wanted to gain speed, so i wanted to gain some power then gear it up a little

[RIDE-RED 250r]

That 38 PWK/AS is a good upgrade in and of itself.

Like I said, my old setup was almost identical to what you are doing. Only difference was I was running a different brand reedblock and the high compression head gasket. Make no mistake, it was fast on top with plenty of top speed, but you could definitely tell it was happiest and pulled hardest through midrange.

I think you will be happy with that setup you are building. Believe me, it will still have plenty of top speed. Leave the gearing stock and see if you like how it runs. I bet you will. After all, you are setting up for having the most power on midrange. Gearing up will start to counter-act what you are setting your engine up to do best at.

Build your engine as you plan to with the spacer, but leave the sprocket gearing alone... I think you will like it. ;)

[william16339]

haha thanks alot man :) high compression head gasket? ware do i find one? isnt it just a thinner gasket? and does it efect reliability? one last question..how fast do you think your old set up was? like the one thats identicle to mine? im JW im not looking for speed to much but im just wondering

[RIDE-RED 250r]

One other thing I forgot about, mine was bored .050, but that really doesn't make much difference. Stock porting...

Yes, it's a thinner head gasket from a cr250.

Reliability was fine. It required a 50/50 mix of 93 and 110, but I ran straight 110 due to the ethanol fuel being all thats available in most places here in NY and I didn't want the ethanol headaches my my baby.

As far as top speed...

My brother in law has a LTR450. Bone stock except for 20" rear tires (stock is 18") It seems from what I hear/read, in stock config that LRT was good for at least 70mph. With his rear tire size increase to 20" I would guess 75mph, maybe a touch more.

On my old setup, I was actually geared down 1 tooth on the drive sprocket. We got side by side on a long gravel road. We both pinned it, I let my R wind up pretty good. It was still slowly gaining RPM but it gets to a point where I don't like to hold it too long. His LTR just kinda walked by doing maybe 5mph more.

So, mine was geared down and I feel it was good for about 70mph as it was. Stock gearing you could probably add about 3-5mph to that.

[william16339]

oh well i dont want to run race fuel lol, but oh ok,,,thanks and wowo..i though stock 250s go 79 stock? and when my 250r was stock ( no pipe or nothing) i got on video of me racing a 450r and the 450 got a 15 foot head start and i still won bye a few feet...,my 250r wheelies in 6th gear...most dont, my friends dosent, so idk whats wrong with my trike but its fast and theres nothing done to it lol..stock gearing too..soo

[pcs]

stock 250r will not go 79mph, dirt wheel mag tested all the 2 smokes back in the 80s and the quadzilla had the highest stock speed of all in 100% stock trim and hit 79.xxmph on the 1/4 mile.from experience, when you mix and match parts that dont complement each other you end with a expensive turd. by no means am i calling your set up a turd or mean any disrespect towards you. by that i mean that you will end up putting lots of pricey parts in a motor that might not perform well. parts that are designed to low speed hp will not work well with parts designed for high rpm hp. if you want more speed, aim for higher hp, if you need "torque" or "down low" power, just down shift, and put your motor in its power band and gas it. the 2 250r's i put on a dyno, atc and trx both lost overall power with a spacer. the spacer increased hp around 1/4 to 1/2 of the rpm range then after that started to choke both engines. on the atc it also caused fitment issues with the intake tube bc it placed the carb to close to the rear shock. good luck on your build.

[william16339]

really it chokes it up?

[NOS_350X]

All a reed spacer does is add to crankcase volume, If you run a spacer for a long rod/stroke i would never even consider it. if you dont have a spacer you can use it to get to a desired point of your crankcase volume. This should all be calculated out by your engine builder.