Low Tech, Lightweight 4-stroke engines?

Discussion in 'Some Assembly Required' started by tdvt, Jan 30, 2013.

  1. tdvt

    tdvt Been here awhile

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    Can't stop thinking about a really light woods bike project, especially after seeing this one in another thread.

    Nothing against the Honda motor, but I am not familiar enough with all the stuff that's out there so I thought I'd ask what other engines are comparable to the XR200?

    That being; air-cooled, 4-stroke, six-speed, reliable, lightweight package, reasonable power, parts availability, etc.

    Any others out there?
    #1
  2. aposaric

    aposaric Garden mechanic ;-)

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    http://www.bikez.com/motorcycles/yamaha_ybr250_2011.php

    First thing that comes to mind is a Yamaha 125 or 250 cc engines that comes in their cheap YBR models. This engines are indestructable, there are a lot of people traveling around the globe on them, some have more than 170.000 km on them and they are still going strong. Only downside is they are 5 speed.

    Fuel injected (100 mpg), 20 ponies, featherlight and dirt cheap to buy and maintain.

    Honda also has some nice 250 cc in their hornet but that is liquid cooled so it makes things little more complicated and heavier :-)

    cheers

    a.
    #2
  3. kellymac530

    kellymac530 motorcycle addict

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    The Yamaha 225 motors are not super powerful, but neither is a XR200.
    The Yami 225 came in the XT225 and in the Serow model. Not sure where yo are at, but it may have a different name where you are at.

    Full wet weight for a newer Yami YZ 125 is 208 lbs..
    I would really like to see that Honda on a scale...wet.

    The YZ125 is about as fun of a bike as EVER built and has some of the best suspension imho. The suspension on that Honda looks sub par for any serious off roading by an adult...but we all like different things, so I can not say what your needs and wants are. I agree that I would like to ride that Honda...small light bikes are always fun.
    #3
  4. dentvet

    dentvet Long timer

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  5. tdvt

    tdvt Been here awhile

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    Thanks for the suggestions. Coincidentally, I was thinking of the YZ125 as a platform but don't really want a 2-stroke hence the engine question.

    At the moment I have a TTR250, which is plated here in VT, so I can link up trails & not worry about being hassled. I really like the air-cooled simplicity of it & also the 6-speed but while not a pig, it is a bit heavy. The e-start is pretty nice too but I could live without it if I had to. Something with the same or a little less power but a lot less weight, would be perfect.

    It's always interesting to see what people are using on the 'round-the-world excursions.

    I found that same info about the XR motor. Best estimate I have on my TTR engine from others, is around 80lbs, quite a bit heavier.
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  6. kellymac530

    kellymac530 motorcycle addict

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    The XR200 motor is substantially smaller in external dimensions and in weight than the TTR225/250 motor. Not sure why, but those Yamaha motors are pretty beefy for an air cooled simple 4 stroke engine. They are pretty bullet proof though.

    It seems as if you are ok with a smaller framed bike {that BBR is a small frame for 80-105 class bike I believe} then look at a Honda CRf150 R....not the F model. That little bike is pretty sick, crazy light, VERY high powered, well suspended and they make springs for the fork and shock for adult weights for them....I do however think you are talking about building something yourself...that is more fun and rewarding.

    http://www.honda.com/newsandviews/article.aspx?id=6033-en

    The expert model has the big wheel set up {19" front, 16" rear and the standard has the 17/14 set up}
    I have a few grown men friends that race those here in So Cal...they are really fun. The put taller bars, a taller seat, heavy springs and tear it up. A bit high maintanance though compared to say and XR200 motor.
    http://www.motorcycle-usa.com/2919/Motorcycle-Photo-Gallery/2012-Honda-CRF150R-First-Ride.aspx
    #6
  7. Salsa

    Salsa Been here awhile

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    If I remember correctly my XR200 motor weighed 65 Pounds.

    Don
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  8. kellymac530

    kellymac530 motorcycle addict

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    The comparison in that link to thumpertalk is actually not as far away as you might think, unless he planned on bump starting it. He was comparing a 230 with the starter motor mounted on it, but the 200 motor had NO kick start arm on it...not that a kick starter is super heavy, but it is at least 1-2 pounds probably...maybe you could find an aluminum one that fits it to save some weight, but I am just saying that the comparison is not apples to apples...not quite apples to oranges...maybe apples to pears...? :lol3

    Keep posting what your ideas are... I am interested in the project.
    #8
  9. dirt hokie

    dirt hokie Been here awhile

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    i have a simular plan when i have the $.

    thinking yz 125 + xt 225 = light weight trail bike with e start good suspension and light weight. Would also consider a ttr 250 motor if the weight is not much more. What does a YZ 125 weigh, 200lbs. SO i think 225lbs might be doable, if i keep the steet equipment to minimum.
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  10. kellymac530

    kellymac530 motorcycle addict

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    If you can street plate a YZ125 frame in MD then that is awesome. We can not here in Californiakistan. Wouldbe nice.
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  11. tdvt

    tdvt Been here awhile

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    I think the older steel-frame YZ 125's are listed at 192lbs/dry. Have you found out what an XT motor weighs? I think they are a little bit different than a TTR but I'll bet there's more aftermarket stuff out there. Be interesting to know.

    Hadn't really thought about dismantling the TTR but I have wanted to upgrade the suspension. Might be easier to just transplant the motor to a YZ roller. Don't think it would be much lighter though.


    It's not uncommon to see plated YZ's, WRF's or 2-stroke KTM's over this way, though you wonder how long it may last.

    There is THIS THREAD in Thumpers, basically told the DMV it was a custom build. That would actually be the case with an engine transplant. I feel for you guys in California, sounds like there are no loopholes left.
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  12. dirt hokie

    dirt hokie Been here awhile

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    you cant plate a yz, but i would get the xt plated and then basical ......

    Or graft the head tube with the vin onto the yz frame and then adapt the yz forks and tripple back onto the xt head tube, just to make the vin # legit. .
    #12
  13. bkowal

    bkowal Been here awhile

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  14. kellymac530

    kellymac530 motorcycle addict

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    I would not tell you not to do that...but I do know that any vin modification is a crime...I believe a FEDERAL crime. Just sayin, if you go that route I would be very careful...especially posting that in a public forum...:eek1
    #14
  15. dirt hokie

    dirt hokie Been here awhile

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    it would just be a modification to the frame. No differnt then building a trike from a harley and Vw and calling it a motorcycle, instead of a vw behind the small bit of harley and the vin it would be a yz 125 frame.

    i wont worry until i have the $ then the real research can begin, if i cant make it under 225lbs it theres not much point. I would just find a plated ttr 250 and put yz suspension on it and cut as much weight as possable and end up around 250lbs.

    i already have a plated xr 400 thats around 275-280ish, but i would like estart and better suspenion.

    I like the idea of building a usefull bike that is unique. I could also start with a plated ktm frame but would be called crazy for wanting to put a low performance motor in it.
    #15
  16. kayaker43

    kayaker43 Adventurer

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    That's my reworked BBR posted above. After more mods its right at 180 lbs wet but no gas. I have essentially the same suspension as the CRF150R and very close on the weight but its a bigger bike.

    The XR200 motor is in a class of its own regarding small simple four strokes. Nothing else can match it when you look at the whole package. When bored and stroked it has gobs of mellow meaty torque that is so fun to ride with a wide ratio six speed. A CRF230 engine is a modernized version but 12 lbs heavier with E-start. I built up a frankenstein motor with XR200 six speed kickstart bottom end married to a CRF230 crank and top end. This is not a bolt together project but can be done. I still need to build a crank trigger ignition before I try it out.

    The closest thing going is a CRF150R but its not adult sized, and it has peaky power and short engine life compared to an XR. If you could enlarge one and lace up bigger wheels it most likely would weigh more than mine. The race tuned engine and close ratio gearbox wouldn't make a very good dual sport either.

    Honda could easily build an insane playbike or small dual sport just by mixing up parts they already have.
    #16
  17. CharlieT

    CharlieT old school

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    If you want something with a bigger frame and adult capable suspension, you could always start off with something like a CR250 or a CRF450 chassis. My son and I are both 6'-6'1", so a larger frame was much more comfortable. This is our street legal what we call a CRF200R.....CRF450 chassis with an XR200 motor.

    [​IMG]

    The harder you ride it the better that suspension works. GPS top end was at 72mph, but you could still plonk around at walking pace with no problem. Weight at around 225, full of fuel.
    #17
  18. tdvt

    tdvt Been here awhile

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    Love both your bikes. I saw your CRF-based bike in another thread.

    From my limited research, it sounds like the XR motor is the way to go. I was wondering what year engines you both used as I did find info about a less-desirable version, made for few years in the mid-90's?

    I am not quite 6' but would prefer a more full-sized frame. If I start with a frame from a bike less than 300cc's then I avoid the whole title thing here in VT when registering it.

    225lbs sounds pretty good to me!
    #18
  19. CharlieT

    CharlieT old school

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    Keep an eye out for a CR250 then. Basically the same frame as the early CRF450's. I don't recall the exact year of our motor, but it is an early '80s. Plenty of room for that XR motor in them.
    #19
  20. Dryslick

    Dryslick Adventurer

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    Both the 150 and 450 conversions are nice. I started an xr200/rm125 project last year, but haven't gotten to spend much time on it in the last 6 months. This thread has got me wanting to get back after it.
    #20