A forum for owners of Yamaha TTR250 trail and enduro bikes!

 

The wheels seem ok as well, except for two dents in the rear rim. The tank had been repaired in the past and it wasn’t pretty, but it was not leaking. The forks seemed straight.The engine ran and I could ride up and down the street to check that the gears and clutch worked OK.

Wow that tank has had a hard life!
Everything is fixable - the skill is in not spending a fortune in the process.
Good to see another resto thread. Been quiet here for a while. Keep the pics coming,
Simon.

 

I don’t have access to sand blasting here, so we used a wire wheel and sandpaper to strip the frame. I used a primer from spray cans to prepare the frame for the paint and to avoid new surface rust before getting it painted.

 

Next I decided to have a look at the engine for a change. The engine had seemed OK when I tested the bike before buying it, but I still decided to take off the cylinder head and cylinder to check the bore and the piston. The cylinder had been re-bored to 0.50 mm oversize, with the corresponding piston. I did a light honing of the cylinder and installed new piston rings.

 

The camshafts were luckily OK, but the threads were stripped on the bolt holes for the caps, and the bolts had been tightened using small strips of aluminium in the holes to keep them tight. I repaired these with Helicoil thread inserts rather than cutting out strips from a beer can...I did struggle a bit with some of the helicoils and had to pull some out and start again, but that was just me not using the tool correctly. 

I find that using studs with a nut to tighten the cap could be a better solution. The stud would be installed once and for all in the head, and not having to screw a steel bolt in and out of the fragile aluminium threads would be a safer way to tighten the caps in place. Some engines use this solution from factory, and sometimes it is done as an upgrade on racing engines. It seems feasible to make studs that would work. Has anyone tried this? If I run into problems with these bolts again I will check with my local machine shop about doing this.

The valves were in good condition and I re-installed them after lapping them into the valve seats. I then had to shuffle around the shims and order some new ones to adjust the valve play.

 

-- Edited by PurpleWheels on Tuesday 8th of September 2020 08:54:01 PM

 

Suspension was next on my list. By now I had placed my first order to Steve for parts, including bearings and seals for both front and rear suspension.

Loosening the bottom bolts/valves on the forks to take them apart was a real struggle. On one side the bolt head had been damaged due to an impact and I had to use my Dremel to open up the slot for the allen key. Even the use of a compressor driven impact gun failed to loosen the bolt. I managed to find a large 14 mm allen key and with that and an extension arm I finally managed to free up the bolts.

Next surprise was to find that both these bottom valves were damaged beyond repair. Some previous owner/mechanic had jammed a steel rod down the fork leg to keep the internals from turning when tightening the bottom bolt. Not much hope of adjusting the rebound with these. Please note that these are the early model forks, and parts are not as easy to find as they are different from all the later models.

 

The steering head bearings were still fine, so I cleaned and repainted the triple trees and assembled with new grease.

What a great stroke of luck!  Some nice parts in that haul. The panels in particular are now very rare.

Loving your thread - great job and super photos 

With the frame painted I fitted the engine. Nicely tightened down I realised that I could not attach the clutch cable to the actuating arm, which was pointing in the wrong direction, and being blocked by the frame.

I have subsequently seen some warnings about this mistake, i.e. not keeping the arm pointing the right way when lifting in the engine, so I don’t feel too bad about this knowing that I wasn’t the first one. Unscrewed the bolts, tilted the engine, turned the clutch arm, and re-installed everything. Lessons learned...

 

I installed a new chain slider on the swingarm and a new chain roller on the frame. Mine had been set up with some locally developed alternatives, i.e. a piece of cambelt and a rubber exhaust pipe support. Sorry, can’t confirm from which car model in case you’d be inspired to replicate this, but a mid-90’s Toyota Corolla would be a likely candidate. I also added a new frame guard where the chain could touch the frame just behind the front sprocket.

 

Next in order was the electric harness that required some cleaning and repairs. I was able to take some wires from the harness I got from the parts bike, mostly to keep the correct colour coding of the wires.

There were some strange additional connections behind the headlight, and I removed the extra wiring that didn’t make any sense. Everything needed a good cleaning, but luckily nothing was badly oxidized or burned.I was quite happy with the condition of the harness.

 

 

 

The regulator/rectifier was another non original part, see the one on the left in the picture, and the wiring had been adapted to fit it. It looked like a part from some small Chinese bike. Would probably plug straight into the harness of an old Honda 125. I ordered a new original R/R, and found a similar faulty one here that came with the correct connector with short lengths of wiring so I could connect it to the wiring harness.

What they had done basically did work so I could have kept it, but it didn’t really fit the space under the tank and the wiring was not well done. Twisting two wires together with some tape over the wires is OK for testing, but not a permanent fix. It also looked like it may not have a sufficient output in case I would like to add any accessories later on.

 

I had two headlights to choose from, and I ended up using selected parts from both, after some cleaning and painting with a heat resistant paint.

My parts bike had a good magnet for the sprocket shaft and the sensors on both bikes seem ok. I did not install the standard plastic cover, but got instead the compact metallic one from Steve. Much nicer!

The sprockets and chain are 520 instead of the original 428 on Raids. These came with the bike and were good enough for some more riding, except for a new front sprocket that I had to install. I am now riding with a 14-50 combination which seems good for off-road riding. I will probably order a 46 tooth rear sprocket to use with my spare “street” rear wheel from the spares bike.

 

The master cylinder on my bike was from some other bike, probably a Honda street bike with a strange short lever, so I decided to replace it with a new master cylinder made for a Chinese 125 cc knock-off. Looked good and worked well with the caliper, but the lever pointed too far away from the handlebars and was awkward to use. Well, it only cost the equivalent of 5 Euros, I mean the complete master cylinder with even a brake light switch.

The master cylinder from my parts bike was not possible to repair, so I found a used master cylinder from a Yamaha TDR 125 which I cleaned up and installed. Naturally, nothing is as simple as that. One of the screws holding the top was corroded and would not come out by any means, so finally I had to drill it out and tap the hole for an M5 screw. One difference between the master cylinders is the angle of the hose banjo bolt, but it works OK. The lever I got with the master cylinder was a bit bent, but I have a new one that I can install later.

I have the extended braided hose and clutch cable from Steve, for raising the handlebars in the future. I’m 6’4” and need the extra height on my bars for standing up. I am now looking for some used Honda Africa Twin handlebars, which I should be able to find here. They are the same width, but a good 5-6 cm higher and a bit straighter, which I prefer. BTW, the Honda Transalp handlebars are an option too, same height as the AT, but they have a bit more pull-back, about the same as the original TTR handlebars.

 

I could not find a correct sealed battery of the right dimensions, but one mechanic here showed me a 12V battery from an AC backup inverter, which turned out to have the exact dimensions of the original battery. Same 7 AH capacity too. These are found everywhere here due to the use of the inverters for surge protection and power cuts. The only issue was the connection as these have two narrow “spades” next to each other on top of the battery, as opposed to the usual screwed connectors. I had to turn the “top” of the battery facing rearwards, with openings made in correct positions on the battery box so I could connect the extension wires.

I had some fears about the cranking amps of these batteries, but it starts up my engine with no hesitation. Then again, I can’t say for any cold start characteristics, the average temperature here is around 28 degrees C. My other worry was about overheating the small spade connectors on these batteries, but they have been OK even after some extended cranking.

It’s not perfect as I wanted to retain the original battery cables for now, so I had to screw the original and the extension wires together on the outside of the battery box, which together with the strap I currently use hold the battery in place are too bulky to allow the side cover to fit flush. The top front of the cover does not reach the rubber grommet, but the top of the cover still fits under the seat. I will see how to improve this at a later stage, maybe with new longer cables. For now this work well for riding.

 

-- Edited by PurpleWheels on Tuesday 8th of September 2020 08:46:03 PM

Hey, I just work really fast...

I agree on the ingenuity, I will share more examples of that as the story progresses! When you cannot find the right OEM part you have to take what you can find and adapt.

Nice job! Keep us updated.

The carburetor was dirty inside and had some issues. I replaced the float needle and filter, and the pilot jet. The emulsion tube was bent for some reason and looked old and worn, but as I could not find a replacement I just bent the head back straight.  I heated it first on the stove, screwed it back in the carburetor, and put a long 8 mm socket over it with an extension to bend it. Luckily it didn’t break off, it was far easier than I expected.

I still want to find a replacement tube as I already have replaced the needle as well. And a new main jet is also on my list.

One float pin support post was broken and had been repaired with epoxy, which now seemed have softened. I could not find the right type of screws to repair as shown here https://ttr250.activeboard.com/t50560400/carburettor-repairing-a-broken-carburetor-float-pin-post-and/ so I decided to try something else.

I removed the old epoxy and cleaned everything. Then I drilled a small hole with a 1,2 mm drill bit through the post and filed a small groove on the top of the broken piece which had been glued back. Then I pulled a stainless steel wire through the hole and over the top and twisted the wire together. The pictures explain it better.

 

My bike came with a non-original CDI, piggy backed onto the original harness. Four wires were used on this CDI as opposed to seven wires on the original. My guess is that the CDI is from some Chinese CG 125 clone. I managed to find a used TTR 250 CDI here (still can’t believe my luck!) and I wanted to put back the bike to its original setup. The bike seemed to work well with the non-original CDI, but it’s unlikely that the ignition advance curve would be identical to the original, and I had no idea about any rev limiter on this CDI.

Fortunately they had not cut all the wires, but just stripped the insulation and twisted on the additional wires for the new CDI. I took off the extra wires and put shrink tube on each original wire after disconnecting them from the CDI connector one by one. The shrink tube has glue to make it waterproof. Belts and braces...

 

-- Edited by PurpleWheels on Friday 11th of September 2020 12:46:39 AM

 

The second engine’s flywheel looked much better, the small flywheel puller fitted easily and the flywheel came off. However, the backside was a disaster. The sprag clutch, also a non-original, had been welded on to the flywheel, and not very professionally. No TIG weld with a nice flowing stack of coins here… Another issue could be the balancing of this setup. A few grams here and there rotating at 8000 RPM could cause some vibration.

The second picture shows the metal strip on the side of the flywheel that triggers the CDI. This has not been modified. The flywheel has some nice patina...

 

 

-- Edited by PurpleWheels on Friday 11th of September 2020 02:18:55 AM

 

I removed the flywheel from the engine on my bike and took off the sprag clutch. At that point I realised that even this was a non-original clutch, although much more like the original one. The main difference was that this clutch was attached with three 8 mm bolts, but the distance between centers fitted exactly the original holes.

I proceeded to enlarge three of the holes on my now repaired spare flywheel to 8 mm, bought three M8 x 20 allen bolts, and put everything together. The 8 mm allen bolts needed their heads to be reduced by about half a millimeter in diameter to fit the slots in the flywheel. Obviously 6mm bolts have smaller heads than the 8 mm ones. I used a grinder, rotating the bolts to keep the heads round(ish). Did some quick manicure in the process. Method not recommended in any OHS manual, better to use a file or a lathe.

Flywheel cover on, oil in the engine, connected the new CDI and it started and ran perfectly.

 

 

 

-- Edited by PurpleWheels on Friday 11th of September 2020 02:04:30 AM

 

With my parts bike I got a small rear carrier which seemed quite OK under all the rust. I cleaned it up, straightened and painted it, and it fits the bike perfectly. I don’t know if this had been made locally or if it is something that were sold as accessories at some point. I did not find anything indicating a brand or a manufacturer. I can use it to add a small top box to store my rain gear or my helmet if I want to use this for commuting at some point. Normally I commute on my Yamaha Xmax scooter.

 

-- Edited by PurpleWheels on Friday 11th of September 2020 02:06:25 AM