Yamaha TT250: The quest for the perfect trail bike

yamaha-tt250-rear-leftActually, there can't be a perfect woods bike because there are different classes of riders. Intermediate to expert level fellows from 25 to 45 with abundant testosterone are perfectly happy with KTMs and the like with sky-high seat heights and more than needed power. But there's another bunch of riders who appreciate a scoot a little closer to earth with tractable power--novices and senior riders. I am part of the senior bunch and to them I recommend reaching back in time to obtain one of these older bikes and rebuilding it in a limited way. I paid $500 for one in great shape. My brother Ric spent $250 for an XT that needed more work. That's your price range--try to stay in it.

Power and Weight

The TT250 (and its XT250 brother converted to TT specs) have several hidden secrets. They are light at about 236 pounds with the 6.2 pound silencer removed (a CRF230 is 233 lbs). 236 is pretty light for a 4-stroke. They have a low seat height of 33" which makes touching the ground twixt trees easier.

The power is snappy, torquey and it was faster than XRs, DR370 and DS series Suzukis of the time and I think my CRF230 too but I have yet to do a side-by-side check. But before you do thing one--toss the stock silencer. They are heavy and tend to choke off aspiration when loaded with carbon.

Suspension

yamaha-tt250-front-leftWhile the TT250 has positive attributes, it also has two liabilities--one of which is solvable. A limited travel of 8.81" front and 7.5" rear is not solvable, but that's the price of keeping your monkey butt close to the ground. This is not huge-just stay out of tall air. The other is a soft play-bike suspension. This is solvable. Get a RaceTech or similar heavier fork spring kit and add 10cc to 15cc more of stock weight fork oil as Super Hunky recommended in Dirt Bike magazine. I found a local shock expert, Tommy Mason, who was able to add a remote adjustable reservoir to the stock rear Monoshock. He just popped out the fill plug and added the remote. Now the rebound is clickable. Those two things cure the sloppy stock suspension.

That's really all you have to do with this bike. Oh yeah--get new rubber. Old bikes with old frame geometry need all the help they can get. Tires can help big time.

Performance Enhancements

I got in a little deeper by enhancing carburetor performance with kits from Thunder Products--their Dial-A-Jet and Quad Flow Torque Wing. This is cheap a way to add 4 to 5 horsepower without doing the expensive cam/bore thing. Their kits also increase range. Next year I will do a side-by-side with my brother's bike to illustrate the benefits of kits from Thunder Products.

yamaha-tt250-front-right

I spent the summer of 2014 building this bike. I have yet to get the bugs out but I am looking forward of proving my point about making it the perfect woods bike from old iron next spring. My goal is to make this a hare scrambles mount.

Some of you may poo-poo drum brakes. This is misplaced. If the rear is up to snuff you are okay. Through the trees I rarely use the front brake. You roll off the power and add a little rear stopping and it's off to the next corner. 

After doing indoor pit bike riding two winters ago I learned something which debunks my rear brake use claim. I proved it last spring on my CRF230. Use the front and rear brake. The difference is amazing. You can come into a tight tree-lined corner and quickly stop the bike to a standstill, turn, then fire off in a new direction without having to put a foot down. I spend evenings watching vintage MX videos. I have noticed sticking a foot out in corners wastes time. Your feet are off the controls and your center of gravity shifts to your seat instead of on the pegs. Try feet on pegs more than you do. If you have good rubber have confidence. Take risks--you'll be faster.

Aesthetics

I know you are wondering about that painted tank. Yes it's stock. The magic of old plastic dirt bike tanks is that the plastic dries out so it will take paint. My plan is to drain it after each ride so I don't get gas bleed through and lift the paint. The fenders are CR.

Specs

Frame

  • Wheel base: 56" (less because of leading axle)
  • Seat height: 33"
  • Fork angle: 30° (less because of leading axle)
  • Fork tubes: 36mm
  • Travel front: 8.81"
  • Travel rear: 7.5" (mechanical adjustable preload)
  • Brakes: drum both ends
  • Front tire: 300 x 21"
  • Rear tire: 510 x 17
  • Dry weight: 242 (less 6lbs if you ditch stock silencer)

Engine

  • Displacement: 249cc
  • Bore/stroke: 75 x 56.5
  • Ignition/starting: CDI/Kick

Phil's Hints

  1. If you own or have to buy an XT250 get TT trees and forks from eBay. It's next to impossible to rebuild XT forks and the trees are equally as bad.

  2. If you have comments about your bike that will help others, write litadv@aol.com and we will build a neat little file here.

My mechanic, Sam Niskanen, bought one new and loved it. He said there was a Yamaha bulletin on a valve/oil starvation problem. Do you know what the problem was and the source to fix it? I've tried to run this down on forums but no luck.

TT250 Oil Bulletin

Cory Rich says:

Fix was to put roll pin in crank snout to restrict flow to big end hence increase flow to head. I flat track mine 6-10k rpm so I don't bother. Problem generating bulletin was no doubt riders who slogged around all day at low rpm with dirty 5W-20 Penzoil. Regular top end inspections show no lack of lubrication whatsoever. Cam sprocket bolt will back out, grenading the motor. Call me for an easy fix.

Cory Rich
www.ironmachine.com
ironmachine.com@gmail.com
707-845-7400

Yamaha 1983 TT250 last ride July 2017

I really don’t have time to ride much so the bike has been sitting unused for some time. This July I made the mistake of riding it at an MX practice track. At 75 I’m a terrible rider but the bike was not able to come to my aid. Its suspension was too short. It’s a tad on the heavy side compared to MX bikes.

On the way back from riding I decided this one needed a new home. It really is a cabin bike for enjoying the scenery on two-track trails and that’s not my thing. I pegged a price of $945 on it and I know thats about right because Craigslist callers burned down my phone. I pulled the ad in 24 hours but it hasn’t sold to the guys that called.

It was replaced by a 1991 YZ250 and when I’m done with it, it will appear here in Toys. After all the hopes about it being the perfect woods bike I was totally wrong. My CRF230 is the perfect bike

Yamaha 1983 TT250 Report July 2017

It’s been two years since I bought this bike. On 7/12/17 I got my first real chance to ride it in the worst place possible--on a motocross track. I learned the bike would be much better for a younger person who is shape. I am an old man with a flabby middle and zero strength. It’s a fun bike with a decent power band and it didn’t do all that bad on the jumps--the adjustable remote reservoir helped in this regard. Mind you I am not a big air kinda guy--in fact I am a pussy. Flat trackers don’t learn how to fly. I have determined the bike has to go to a new younger owner who won’t turn into a panting dog using the kick starter after falling over multiple times. Other riders at the MX track were impressed by the way the TT looks for an older off road scoot

Yamaha 1983 TT250 Report February 2016

Got the bike back from my fix-it man, John Metz. As I said he replaced the cam arms and piston which restored the damage caused by the oil flow. As I recall he pounded a 6mm roll pin in the crank end to encourage more oil flow to the top end. That’s where the secret of life for a TT/XT exists... oh and he pounded marks into frame's serial plate and cases.

Yamaha 1983 TT250 Report January 2016

After a last summer's ride the TT250 spoke to me. It said “I ain’t runnin’ anymore” and promptly quit. Happily I was riding on a backyard mile trail owned by my machinist and my mechanic. I rolled into my mechanic’s shop (John Metz’s Some Guy Enterprises) and said “fix it.”

Turns out the frame’s serial number tag was stamped (Yamaha stamped a star over serial number after oil passage modification was made) but the engine numbers weren’t. The engine melted. It needed new rocker arms and a cam. The rocker arms were an easy find on ebay but rather than replace the cam I elected for a hotter cam from WebCam. I bought their 388 grind cam for $180 and valve spring kit with Titanium retainers for $95. That cam is not their hottest but it will boost the entire band and hopefully make up for the gaps in the cog spacing. I figured that as long as I needed a cam why not pop for a hotter one while I was spending.

It turned out I needed a piston too. That I got free from my brother's XT250 which was in the shop too. His engine destroyed itself from the same oil imbalance problem. He had to go 2nd over.

I guess the point of all this is if you are going to buy a TT/XT 250 make sure frame and engine tabs have been stamped so you can avoid the problems we bumped into. I will report back after the first ride in the spring.

Yamaha 1983 TT250 first ride August 2015

A year after I purchased the bike, beautified it and got an adjustable rear shock sorted out I rode it. My quest for the perfect trail bike continues--The TT250 ain’t the bike... at least for an older rider. Here’s what I found riding an extremely tight wood trail with no straight relaxing sections.

The bad

  1. Front has a tendency to wash out. That could be rider or the stock 30° fork rake.
  2. Lower gears have holes in power delivery. Noticeable up hills.
  3. Kick start sucks when you crash on hills. Here’s where a button bike shines.
  4. I think I have the XT/TT oil delivery problem. The bike stopped with ugly engine sounds. Cory Rich’s points above indicate oil delivery is a problem at slower speeds but not in full-on race modes.

The good

  1. This bike will work fine on more open trails and two-tracks.
  2. Younger riders can handle the kick only starting without tiring like old folk.
  3. Seat height is perfect.

When the bike is repaired I’ll report again.

PS: Ghost around in my toys page to see other scoots I have built.

  • [Site updated October 15]