Project CB250RS Restoration/Rebuild

Well, I'm planning on taking her to Tamworth somehow...

 

I keep my riding gear on apart from the gloves and helmet

 

No inspection today, unfortunately while Scarlet idles nicely she dies after a few minutes riding.

Decided to rebuild the carb that's already out and found the throttle sticks really badly.

Also discovered the carb kits I got are also not for the right carbs. Oh well, at least they were cheap...

I'll strip and clean the inside of the replacement carb next week.

 

Ultrasonic Test Run (CB250RS Carburetor Clean & Rebuild Part 1)

After reading a post about cleaning carburetors with ultrasonic cleaners on the 2fiftycc.com forums and having a friend post about having bought one from Jaycar on sale recently, I decided to get one and try it out myself. Here's the one I bought.

For cleaning solution I used water and a few drops of concentrated dishwashing detergent. Processing time was 7:30 per batch.



So far I’ve been pleased with the results.



Before photos are on the left, after on the right









The brass jets came up especially well.









As the cleaner is a very small one (only 550 ml capacity) I had to turn the carb body around to clean it properly.











The whole process took about 90 minutes in batches.
Finally, I put everything away in a box to reassemble later.



More ultrasonic cleaning experiments and rebuilding the carburetors to come in Part 2!

(copied from my blog post of the same name)

 

Keihin PD70 Disassembly, Clean & Rebuild (CB250RS Carburetor Clean & Rebuild Part 2)

After a successful test run of the ultrasonic cleaner, I decided to clean Scarlet’s current carburetor the same way, as she’d been stalling a lot when ridden.



Of course, this meant removing the carburetor yet again so I could strip it.

After removing the carburetor, I set about removing all the parts, starting with the idle screw and top cover.



Next the return spring came out, then the throttle spindle nut and fast idle link were removed.



Next, I removed the throttle link retaining screw.



After this, the throttle spindle, link and throttle valve were removed. The throttle linkage was held on with two screws.



As I was cleaning and rebuilding, the operating linkage was completely disassembled and parts put in a safe place.



Next I removed the choke cable mount. This step is optional – I wanted to clean inside and out.



On the CB250RS, this is just a blanking plate. As I was replacing all the seals, the o ring came out here.



To make sure the float bowl was completely empty and to get to the o ring/washer to replace it, I removed the drain screw completely.



Next was the pump cover.



The accelerator pump diaphragm boot was missing, so water could get in, meaning there was a fair bit of rust in here. I replaced it with the boot from Scarlet’s original carburetor.



The float bowl was next. The o ring seal was so worn that I was unable to remove it without breaking it.



I pushed the float assembly pin out with a precision screwdriver, as there is no retaining screw in this model carburetor.



After removing the floats and float jet, I had clear access to the rest of the jets.



First I removed the main jet and needle jet holder. When removing the pilot screw I discovered that this particular carb had a secondary jet that could be removed, so it came out too.



The float bowl from the working carb is on the left, the faulty one is on the right.



On to the cleaning! As per the test run, I used a few drops of concentrated dishwashing detergent and ran each cycle for 7:30 (the longest cycle on the the cleaner).



I started with the “brass” parts – jets, screws and the throttle linkage.



Next up I did the springs, plastic and rubber parts. I decided not to clean the gasket.



The alloy and steel parts were next.





While I did clean the float bowl and carburetor body, I didn’t get any post-cleaning pictures, as I was keen to reassemble the carburetor by this stage. Here’s a picture of the end result instead:



Reassembling the bike was relatively painless. I used rubber grease on the inlet adaptor and screwed the retaining clip back on.



Next I reattached the throttle and choke cables.





A bit more rubber grease on the air cleaner hose helped the airbox in easily, followed by the battery box.



A little more rubber grease on the air intake.



Battery back in.



Tank, side panels and seat back on and we’re in business!



Took her for a test run and found she kept stalling. On closer inspection this turned out to be major flooding, as I hadn’t replaced the broken o ring seal on the float bowl!



The carburetor is a Keihin PD70 model and it turns out that the CB250RS carburetor seal kits can be hard to find at a reasonable price these days – I ended up ordering one from CMSNL.

As the price was relatively high, I wasn’t willing to pay for express shipping but I needed a replacement seal. After some research, I discovered that the Keihin PD carburetors were used in a linked set of 4 in the CB750A 750 Hondamatic, so I ordered a single seal kit from eBay with International Priority shipping.



I checked against the faulty carburetor before opening the packet, just in case. Sure enough, the float bowl o ring matched, as did the top cover gasket and a couple of the other o rings.



I removed Scarlet’s carb again and replaced the float bowl o rings and top cover gasket. The old ones are on the left for comparison.



I noticed the screws were possibly a bit loose when removing them, so I made sure they were nice and secure this time. After reassembling Scarlet again, I took her out for a quick test ride.Finally, she seems to be running fairly reliably and is almost ready to register!

(copied from my blog post of the same name)

 

Final Tweaks Before Inspection – Scarlet Rides Again! (Part 1 of 2)

Last weekend I went through the very final stages before Scarlet’s rego inspection.

First up – rear brake shoe replacement.







To replace the brake shoes, I needed to remove the back wheel.

This meant removing the split pin from the rear axle nut first.
The multi-grip pliers from the onboard toolkit were just the tool for the job!



In order to get to the rear axle without major space issues, I took the mufflers off.
I figured it would be a good time to fit the exhaust gaskets and replace the missing nuts for the exhaust mounts too.





The nuts came off easily enough



The clamps and flanged nuts for the mufflers. The nuts are 10 mm, for those of you playing at home.



The rear mounting bolts also hold the pillion pegs on.



Mufflers off – these bolts are 14 mm and needed a socket wrench to remove easily.



Once the mufflers were off, I had more room to work.



I took off the rear chain case to make it easier to remove the chain and made a mental note to replace the missing chain case bolt.



Next up I removed the front chain cover.



This chain is a non o ring chain with clip master links. We’ll come back to these.



Before I removed the chain, I loosened off the chain tensioning nuts



The rear brake assembly was next.





I also removed the bolt form the rear brake stabilizer bar.



I removed the axle nut – this one is 22 mm. I realised later that I didn’t need to remove it, just loosening it would have done.



Finally the chain itself could come off. I pried off the clip from the master link with a flat-bladed screwdriver, removed the plate and the master link came out easily.



The chain ready for cleaning.



A closer look at the components of the clip-style master link.



I put the chain in an old plastic bucket and soaked it in kerosene while I removed the wheel.



I loosened off the chain tensioners a bit more until I could swing them down enough to remove the axle retaining plates





The wheel lifted out easily. I took a couple of reference photos so I could see how it went back together after disassembly.





The brake shoes were pretty worn.



The new ones are on the left, old on the right.



Fitted the new brake shoes.



After starting to reassemble the axle, I realised I didn’t have the shoes lined up correctly. They should be flush as per below.



A bit of axle grease to go with the elbow grease involved in all this work!



Reassembly – looks like everything is on the right order!



Lifted the wheel back into the slots on the swingarm and greased the retaining plates before putting them back in.



Swung the chain tensioners back up and tightened the axle nut to hold them in place.



After scrubbing the chain with a toothbrush it’s noticeably cleaner.



Threaded the chain back through the front sprocket and reassembled the master link on the rear sprocket.



A flat-bladed screwdriver is very handy for pushing the clip back on.



(copied from my blog post of the same name)

 

Final Tweaks Before Inspection – Scarlet Rides Again! (Part 2 of 2)

At this point, I was ready to put everything back together, until I noticed the damaged plug from the left crankcase cover.



This could have been a major cause of oil leakage and is pretty much not what I want to see on a bike I intend to ride!



Luckily the left crankcase cover from Bruiser was in great condition!



To take this cover off, I needed to remove the gearshift pedal.





Out came the sump plug.



Good thing I had that bucket handy from cleaning the chain!





Once the oil had drained, I removed the cover. As the stator is attached to it, there was a fair bit of magnetism holding it on.





The old gasket and bolts placed in approximate positions for reference when refitting. Two of the bolts hold the lower chain guard on.

Stator mounting bolts removed.



I figured I might as well replace the gasket while the cover was off. Luckily, I’d already bought a complete gasket kit in expectation of a complete motor rebuild. The replacement paper gasket is at the top, the original plastic one at the bottom.



Bolted the stator onto the replacement crankcase cover and put the sump plug back in before reassembly to save time.



I noticed some corrosion/crud in here and cleaned it out before replacing the cover.



Put the new gasket on.



When replacing the cover, I replaced the washer over the gear selector axle before easing the bottom corner of the crankcase cover onto it.



While replacing the crankcase cover, there was a strong magnetic attraction that “sucked” it into place.



After bolting on the crankcase cover and lower chain guard, I reconnected the neutral switch wire to the neutral switch. It’s held in place with a spring and washer.



The collar for the neutral switch was missing, so I used the one from Bruiser, then replaced the gearshift pedal.



After refilling the engine oil, it was on to the chain. Out with the trusty chain oil!





After oiling the chain and sprockets, I replaced the front chain cover.



Adjusted the chain tensioners to approximately matching settings.



Reconnected the rear brake stabiliser bar and brake pedal



Tightened up the rear axle nut and replaced the split pin.



Finally, I moved on to the exhaust gaskets. At first I thought that there were no exhaust gaskets fitted but they were just completely crushed. The old gaskets are at the top, the new ones are at the bottom.



The new gaskets were a tight fit, so I tapped them in place with a hammer and the extension bar from Scarlet’s toolkit.



I replaced the flange nuts with the new ones from the engine bolt kit I bought months ago but never got around to using.



Bolted the rear mounts back on with the pillion pegs.



With the mufflers replaced, it was time to start her up!



After a quick run in neutral to test her performance, I decided to give her a polish with the towel I’d mopped up the spilled 20W-50 with while replacing her oil. She came up a treat!



Unfortunately after a quick test ride, I noticed that while the speedo seemed to work, the odometer didn’t. As I’m planning to take her on some long road trips, this could be an issue!

I swapped the speedo for another one that had a broken needle and broke both the tacho needle and the speedo needles in the process. The tacho needle was able to be glued back together but the speedo one broke so thoroughly that I replaced it with a piece cut from a broken translucent orange plastic box I had. It’s on my list of “things to fix longer-term”.

The good news is, she passed a rego inspection today so will be registered as soon as possible!

(copied from my blog post of the same name)

 

She idles fine now.

Got Scarlet registered this morning. Put number plate on. Chain came off on the way to work and the rear brake assembly is trashed. Didn't tighten the axle enough .

A guy with a ute stopped and helped me get her home. Luckily I have donor bikes and the pads should still be ok!

 

Thanks for the call on that one @risky - as discussed I think I've got it sorted. Will be rebuilding the rear axle and brake assembly tonight.

 

Preparing Scarlet For A Distinguished Ride

During the epic road trip to Tamworth and back, I found several things that needed attention before I rode Scarlet much further.

The first three I deemed important enough to fix before my next road trip the following weekend – the front master brake cylinder, problems with the lights and the blown fuses.

First I cleared a suitable work space of everything but the triplets.



First order of business was to bleed the leaking master cylinder in order to replace it.



After bleeding the master cylinder, I removed the brake lever and inspected the seal. Unfortunately the pic is a little blurry here – you can still see that it’s leaking if you look closely though.



I removed the master cylinder and left it to drain.



As I had a spare master cylinder with no leaks, I fitted that one, filled it, bled the brake lines and tested for leaks. I found there weren’t any, so moved on to the lights and fuses.



The head and tail lights had failed at night, the instrument lights had gone out and some of the fuses had blown on the return trip, so I checked the headlight first and polished the instrument cluster housing.



Not wanting to take any chances, I replaced all the fuses including the spares with brand new ones.



The old but serviceable fuses went into Eric’s fuse box.



While I was in the general area, I replaced the brake pedal stopper bolts on Eric and Bruiser.



I also replaced the instrument cluster bulbs on Scarlet with brand new bulbs that are 0.5 Watt brighter. The old bulbs went into the sockets for the spare instrument cluster on Bruiser.



With all that done, I was ready to head to Sydney on my next adventure!

(copied from my blog post of the same name)

 

Cleaning Rusted Chrome, A New Speedo For Scarlet And Regulator/Rectifier Woes

Back in October, I did a fair bit of work on Scarlet.

One afternoon, I decided to polish the mufflers.After spending most of the day polishing with NEV’R DULL and aluminium foil, this was the result.



There’s still a bit of a way to go on that…

The same month, I managed to track down a genuine NOS (New Old Stock) replacement speedometer for Scarlet. As you may recall, I had partially repaired the speedo twice already and it seemed to get stuck quite regularly.



The parcel in which the speedo arrived was well-packed to prevent damage. Inside I found the original box, containing a speedometer with 600 metres on the odometer.



The first order of business was to remove the old speedo.

After removing the ignition switch, I took out the mounting screws from the rear of the instrument panel.



Here are the two speedos side by side for comparison. Guess which one is the new one!



Shortly after the photo above was taken, I dropped the old speedo and broke its face.



Not to worry, I still had the new one!



I fitted the new speedo into the instrument panel and replaced the front cover.



Ignition switch back on the back!



Here it is mounted and ready to use.



Just in case I need a speedo for Eric or Bruiser, I glued the old one back together.



Later in October, I received what I thought was a simple plug-in aftermarket regulator/rectifier for Scarlet.

First up, I removed the old one.



The new regulator/rectifier looked pretty much like the old one at first.



The seller had listed it as being a direct replacement for several models of older Hondas, including the CB250RS. Unfortunately, on closer inspection I found that the connections were completely different and one wire was missing completely!



The old one went back on for now. I’m still looking for a suitable replacement or NOS regulator/rectifier. The lesson learnt here is to ALWAYS check what the old or missing part should look like before ordering a replacement.

(copied from my blog post of the same name)

 

Yeah she needs some attention in the top end but she made it Tamworth and back last year!