1991 Yamaha SR250 - Another Lil' Thumper

greensurfer

New Member
Just bought my first ever bike (turned 40 last year) and I have decided to convert into a tracker/café bike. Was pretty expensive at $1900 NZD but only had 1 owner and 14,000km on the clock. I had been advised its best to start with a tidy bike. Seemed a shame to pull it to bits as it ran perfectly. Anyway this is a before shot.
 

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wicked find. these little bikes are amazing

Great little number, shares a lot of parts with the tt250 and xt250 of the same years. I changed the head gasket and valves in a few hours in our driveway. Lots of pep. my wife loves it.
 
Here is the bike partly stripped. I sold the seat and side covers and will try and flog off some other unwanted parts later. My first purchase was 2 18" rims which I am getting laced locally. First I have to polish the hubs so I need to buy a bench grinder and polishing wheel. I figured I would start with the wheels so I can see how the bike will sit. I will drop the front forks and put longer rears on to flatten the profile.
 

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I have looked at plenty of other bikes. These are a few that I quite like...at the moment.
 

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There has been little progress on the bike lately as I have been spending my time building a workbench (bought the timber for it 3 years ago!), and a bike stand/box out of some left over plywood I had. Its upside down in the pic.

Also spent $400 on a used welder (now I need to learn how to weld), and another $400 on a 10 inch bench grinder to polish up the hubs. Started doing the job today and now realize its going to take a lot of time to get them polished properly. Its all the grooves in the hubs that are proving difficult to get at. Any suggestions? I bought 3 wheels. A sisal, stitch mop and dolly mop but they really only seem good on flat surfaces.
 

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Good luck with the build, here is my almost finished SR250: http://www.dotheton.com/forum/index.php?topic=38765.0

I have links to manuals and wiring diagrams if needed.
 
I am barely a month into my build and I have gone and bought another bike project ! My wife, needless to say, is not pleased. I just couldn't resist as I originally wanted an SR500 but, as they are like hens teeth in NZ, just couldn't lay my hands on one. It came with the original seat and bars and an extra exhaust. Its a Jap import 1979-83 model and judging by the chassis number probably 1980. Has no engine number which is apparently common in Japanese models. Set me back $2k which seemed fair but what do I know. It only has 33k kms on the clock too.
 

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Finally got my wheels back from the guy lacing them. Took months ! Anyway this is the kinda stance I am going for. Can anyone see a problem with me lowering the front and raising the rear. The mock up bits of wood are 335mm where as it had 295mm rears as stock.
 

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Looking very very nice mate. It's good to see a great bike in progress. As for the stance, it looks perfect (very similar to mine, shocks bigger, forks dropped e.t.c) The only thing you should have to do is cut off and reposition the lug that holds the rear brake spring. I cut mine off and put an Allan bolt into a hole I drilled and tapped. Let me know if you want a pic. Keep up the good work - have you bookmarked - oh and plenty of pics please.
 
greensurfer said:
Finally got my wheels back from the guy lacing them. Took months ! Anyway this is the kinda stance I am going for. Can anyone see a problem with me lowering the front and raising the rear. The mock up bits of wood are 335mm where as it had 295mm rears as stock.

There's not a "problem" with lowering the front/raising the rear, but remember that it changes the geometry and thus the handling of the bike. This little excerpt makes sense of how your stability will be changed. High speeds will be less stable when you change your current setup. I can't define "high speed" as I think it is different for each bike. But here ya go...

Rake is often called fork angle, but that is a misnomer. Rake is the angle, in degrees, that the steering head of the frame—not the forks—is tilted back from the vertical. For example, the rake angle on all the Harley-Davidson Touring models is 26 degrees. Generally speaking (meaning there are exceptions) the greater the rake angle, the more stable the motorcycle is at higher speeds. To better understand this, visualize a motorcycle with 0 degrees of rake, with the forks straight up and down, perpendicular to the ground. Ride something like that much over walking speed and you’ll be introducing your face to the ground. Now consider the other extreme; forks kicked out like those of an early ’60s chopper. These bikes were stable at speed, but required a couple of ZIP codes worth of territory in order to make a U-turn. Additionally, at low speeds it’s difficult to keep these motorcycles upright as all they want to do is flop on their side. Taken from here : http://www.ridermagazine.com/motorcycle-features/understanding-motorcycle-rake-and-trail.htm/

Neat looking ride though. I'll be watching for sure.
 
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