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Discussion Starter #1
i am starting to build a drag bike with my stock frame and want to know if anybody knows anything about building this motor. i would like to know what kind of compression to run, jetting and timing if needed. my intentions are to have a 60 plus horsepower 250 and i think that it is possible. please give me some advise
stock frame
-86 bottom end and cylinder stock bore and stroke
-drag ported more than likely from c-leigh
-40mm lectron Alcohol carb
-pyramid reed cage
-cool head if needed?
-Drag pipe recommended by the porter
-Wet nitrous system
 

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if looking for 60 plus horsepower ..I would suggest you consider an aftermarket big bore cylinder as opposed to the stock 250 cylinder ...& you may even get more hp. depending
 

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Discussion Starter #3
if looking for 60 plus horsepower ..I would suggest you consider an aftermarket big bore cylinder as opposed to the stock 250 cylinder ...& you may even get more hp. depending
we are but we are going to learn the funny fuels on a stock jug so we dont end up destroying a nice 350 cylinder
 

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Here are some dyno graphs from some engines that my engine builder, Bob from RB Racing, has built. The specifics are given on the graphs. First one is stock stroke, drag ported and the second one is a 4mm stroker. This should give you an idea of what you can get out of a stock stroke, drag ported R with many bolt on modifications. I'm not familiar with alcohol or NOS, but you're going to have to find a way to get about 10 more horses to reach your 60hp.
 

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well from what i know, alcohol gives anywhere from 12-18% increase in performance. add another 10 to 15 horsepower shot of nitrous and i think it can deffinately get 60 if not up to around 65 maybe more but i havent done this before but will have excellent help we will see
 

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well from what i know, alcohol gives anywhere from 12-18% increase in performance. add another 10 to 15 horsepower shot of nitrous and i think it can deffinately get 60 if not up to around 65 maybe more but i havent done this before but will have excellent help we will see

rb has done 3 of my motors great work good price
i have a 40 mm lectron on meth 4 sale there a guy at silver lake running a 295 on meth 76 hp but its at wits ens as far as porting its a runner hes had it in the low 4s ive seen it !!
 

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well from what i know, alcohol gives anywhere from 12-18% increase in performance. add another 10 to 15 horsepower shot of nitrous and i think it can deffinately get 60 if not up to around 65 maybe more but i havent done this before but will have excellent help we will see
Alky only gives you around 3hp more to the wheels on a dyno. Trust me, I tried it on my 370 after it was built. I got just as much hp from oxygenated race fuel, and didn't need to worry about purging, changing plugs after every purge, etc, etc with alky. Alky is much much harder on the bottom end than race fuel, as well as everything else so purging must be done if the bike is going to sit for any more than 1 day without the engine running. Not to mention, many do not spray nitrous with alky, you will need a nos controller when you spray so that you spray with gas or an have aux tank. Main reason (I guess) has something to do with the flash point of alky does not accomodate NOS, and something with the timing. If you are dead set on spraying, make sure you have a high compression ratio, like 13:1 or 14:1 becuase NOS likes compression.

As far as a cylinder, sure you can make 60 HP out a a stock cylinder, but even then you are pushing it. The stock cylinder can only be pushed so far before failure, and anything over 60 HP is a disaster waiting to happen, IMO especially if you are spraying. Watch how big you go on the bore because they leak. I have seen (and run against) some awful fast triple exhaust port OEM R's in the past. You might want to look into that. I would definately run a cool head, or at least get your stock head O-ringed.

As far as reeds, I have never seen anyone using Duncan/Pyramid anything for drag racing, and I think there is a reason for that. I would run either a V-Force CR250 style reed w/ a 3/8" spacer or ESR billet reeds with the spacer block. You will have to experiement with the reed spacers and see if they work for you. Some like them and some don't. Personally, I have always run one.

As far as an ignition, If you are serious about drag racing, then buy a CR 250 ignition from someone like ESR. Especially if you are going to be running alky. Some like PVL ignitions for alky, but they are not as user friendly or "plug and play" like an ESR. With the ESR CR250, just bolt-on and go. A lot of people have had problems with PVL's on R's.

As far as a drag pipe, You have a number of options. If you are going to stay with a stock cylinder, I wouldn't waste your time with an ESR TRX-11 or FTZ fat inframe, they will be too big for your set-up. I would either run a Sparks TT, ESR TRX-5, or maybe get a Shearer out-of-frame made for your motor. FTZ out-of-frames are ok, but wouldn't be my first choice if I were you.

What are you looking to get for times in 300 ft, just out of curiousity?
 

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Discussion Starter #9
first off thank you very much for all of this input. i live right beside busco beach and am out there every weekend so it will be more for around 600 ft. hard packed dirt and sand. everybody out there has nice 450's, banshee's and street bike hybrids and there are a lot of very fast bikes. i know i cant mess with some of them but i want to be able to beat nicely build 450s and banshees. i have a mx 250r that is a stock cylinder with a nice port job cr250 reed cage 38 esr mikuni and an sst ffm pipe this will beat all stock and piped 450s and banshees maybe i should just lay off the nitrous i kinda want to run alcohol since pretty much all two stroke drag bikes run on it so it has to run better and i know it runs cooler. plus race gas is stupid expensive. what compression would you run? i really just want to build a very fast reliable stock 250r because its easy to make a big bore fast and everyone has a 4 stroke(i really just want to frusterated gettin beat by a little 250
 

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I stopped even considerring getting more power from "funny fuels " when my buddy's brand new built motor was destroyed 3 seconds after hitting the "button"
..I just wanna say good luck & hope ya have a good supply of spare motors & parts !!
 

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i would stay away from giggle gas. its some funny stuff if you don't have ant experience with it the main reason someone run it is because they don't know how to build a good motor that will lay down so good numbers. there are some people in the gas and diesel world that run it because they have maxed everything else out which is ok. and your reliablity go out the do run you run that stuff on anything.
 

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DON'T RUN NITROUS !!!

I have ran it, I have destroyed with it. LONG STORY.....BAD.

Ok, Methanol gives more HP and cooler temperatures, but it takes away some bottom end. I have had really good luck running 15% nitro methane with methanol. It is necessary to use Benzine when mixing the two to attain enough oxygenation to prevent predetonation. I run Klotz two stroke mix @ 20:1 and I have been running it for years. I have had very little trouble and no excessive engine wear using this. I ran micro sprints for a few years and well, everybody was cheating anyway. I suggest installing an inline water temp gauge, it helps with tuning and jetting. I am currently running this in my ESR 310 and it made 72 hp on the dyno. Running my Laeger trx against a full drag ESR 370 and I lost by one bike length. It absolutely eats 450's. I originally ran this in my sprint with a stock cyl. at .120 over with a CR head and a 1986 RM250 head gskt and two base gskts. it was 68 hp on the dyno. I blew it up several times by overrevving it. Watch your porting too many rpm's will kill the piston. OH, in a drag situation you need to get a larger fuel bowl or run a fuel pump. In a 600ft run, if it sucks the bowl dry, it will obviuosly run lean and inadvertantly cook the piston..... I run big jets on a 41 mik.
 

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Discussion Starter #14
thanks maniak. i think you are pointing me in the right direction. one of my buddies has a 200 blaster that is a 200 that runs on nitro/methanol mixed and it is one bad little machine beats 450 all day. its hilarious because they get soo mad. so with an 86 motor setup what do you think i should do with compression and my gasket situation. yours sounded like it was a fast bike. im a parts unlimited dealer so i can get anything i want with ease and for CHEAP. ill be running a fuel pump. and for the other guy, i know a puma motor is fast, and a couple g's along with all the other big bore cylinders ill do that later but for now i am building a 250 so i can learn all about this stuff and not waste my money and be done with it on the first day. i want them to THINK that they are gonna beat me not the other way around im also building a 4mm stroker motor and i know that should go in the drag bike but that is goin in my all around bike. my rod bearing went out two rides after redoing my top end......ahhhhhhh i cant complain though because it has been an awesome motor for three years never had one promblem or one break down ALWAYS SITTIN AROUND FIXIN ALL MY BUDDIES 4 BANGERS AND THATS THE TRUTH.
 

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Maniak, you run the nitro/methanol mix when duning too or just for drags?
 

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Ahhhh, Busco, if you play you got to pay.

What ever you build, if you start out running everybody, ol big pockets Lewis will go buy something that will pass you by or either he'll buy what you got.

Neil
 

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yeah i would love to beat his banshees but i aint even messin with him i want to run with his white and blue 350 but as for the 535 powervalve thats later down the road thats why im trying to start off small i love watching the big bike i have a video of it standing up in fifth gear 600 ft down the track and i mean STOOD UP going at least 80
 

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Discussion Starter #18
i know that methanol is tricky but ill get it all your drag bikes dont run on it for no reason im a fast learner plus i build nitro remote control cars that will do over 100 mph so i know how touchy it is (i also know that aint the same thing either)
 

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Michael 88R, I use the fuel all the time, it's all that I run..... The bad thing is, ridability for duning is not the best, it's all or nothing. I ride "full chicken" most of the time anyway so I like it. The bad thing is that I have it jetted so fat that it loads up when I'm riding with my wife on her DVX 400. I'll putt putt next to her for about 1/4 mile or so and then I have to hit it to clean it out. I can fix it by leaning it out but I don't want to worry about the piston.
 

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teddy if you were only getting 3 hp on the dyno with your 370, i would be curious to as why....???? that does not sound right?? what i have found is that alky likes a load....as most dynos are not an eddiy current dyno, so they are free rolling drums. by just switching to alky, nothing else done at all, i was able to pull 5th gear at fallon....when on gas i could not pull fifth. i re geared it to just pull fourth harder after that tho. you can run much more gear with alky, because it creates alot more torque. There is only one "race gas" out there that i know of that will make the same power as alky, and noone has mentoned it yet......and i will not say,, :) sorry..... good luck with the build, i want to build a 4mm oem cyl one day as well...just got hooked on all the BIG stuff!
 
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