Hazard Marking, More About My Compressor, And CB250RS Cylinder And Seized Piston Removal

Happy New Year!

I took last week and yesterday off from posting due to Christmas and New Year, but I was able to get a few things done over the holiday period.

Firstly, I got sick of hitting my head on the shed doorway, so I decided it was time to remedy the situation.

First up, here’s the doorway in question from outside and inside the shed.

I measured the height from the highest part of the threshold and found it to be exactly 170 cm

As I’m 183 cm (about 6 foot) tall, this is low enough to be a real hazard for bumping my head on. Fortunately my local hardware store sells reflective hazard marking tape. Here’s the view of the same doorway from inside and outside the shed now.

Next up, while I was using the air compressor to inflate the tyre on one of my wheelbarrows so I could do some work in the garden I decided to use the compressed air gun to clean some cobwebs out of the compressor itself. The brown acrylic paint started coming off some parts of the motor (mostly the plastic ones) but I noticed something new on the electric motor – a brand name!

A quick Google search told me that CMG is an Australian company that still makes electric motors. I haven’t had any luck identifying the motor model yet though.

Finally, I decided I was sick of working on Scarlet’s carburetor, so I decided to move onto the seized engine.

The two remaining mounting bolts for the cylinder were easy to remove.

The cylinder itself came off very easily too.

Inspecting the barrel didn’t reveal much at first glance.

Looking at the piston told another story, however!

It turned out the piston was seized to the dowel mounting it to the conrod.

As it wasn’t moving back and forth freely, there was some severe scoring on the outer side of the piston, most likely caused when the motor was turned over after it had seized.

With the piston free, I was finally able to maneuver the cam chain out.

I had another look at the inside of the cylinder and sure enough there was some nasty scoring on the outer side too, while the rear was relatively unharmed.

I removed the piston rings as best I could and cleaned the piston a little to look at the damage again

After only getting one circlip out and finding the mounting dowel to be completely immobile, I decided to use a hacksaw to crack the top of the piston open. After that, I was able to wedge a screwdriver in and split the piston completely.

I noticed some numbering “471” and “1” on the side opposite the “HON” and “DA” – this might indicate the original size or part number.

The conrod and mounting dowel seem to have seized together too. If this motor is going to run again, it’ll need a re-bore, oversized piston and most likely a new conrod as well, as I was a little overzealous with the hacksaw and left a few lines in the top of the conrod!

That’s all for now, regularly scheduled updates will return next week. The next update will most likely be an update on how Sylvie has handled not being ridden for nearly a month. I’m expecting a flat battery at the very least!


Melting Glue, A Solution, Starting CB250RS Engine Teardown, And Some Rubber Grease

As predicted, the mornings were much colder over the last week. I found that while the  grips were quite secure when turned off, the contact cement melted whenever they were turned on, creating a safety issue as the grips then rotated freely around the handlebars!

I decided a better method of attaching them was needed, so I did a bit of research and found that other riders had reported success with both high temperature gasket sealant and J B Weld. I decided to go with J B Weld, as I have used it for fairing repairs in the past and had some already on hand.

On Friday morning, I managed to drop Sylvie while making a u-turn on the way to work. I overshot the corner and got the front wheel caught in a ditch next to the road!

Luckily, I wasn’t badly hurt, and there was no damage from the drop apart from the right mirror and master brake cylinder needing to be twisted back in place. Unfortunately, I didn;t catch any of this on the GoPro, as it ran out of space and stopped shortly after I left that morning.

I’m not sure if the melted glue contributed to overshooting the corner. Needless to say, this made me even more determined to make sure the grips were properly attached!

I turned the grips on for a few minutes first to heat them up.

I took off the bar end weights and they slid right off! The handlebar under the left grip was totally clean, while the right one had a few burnt pieces of contact cement left on the throttle tube under it. I stuck them all together to clean up the throttle cylinder.

I thoroughly cleaned the inside of the heated grips and the throttle tube with methylated spirits.

I found the J B Weld and some scrap cardboard to mix it on.

I gave the left end of the handlebar a good coating.

I put a little J B Weld inside the left grip for good measure


Then I coated the throttle tube with J B Weld too.I left a space at the end to allow for it to spread when the grip was fitted.

I ended up getting some JB Weld inside the throttle tube, so I dismantled the right switch block so I could clean it off before it set.


I ran the bike for a few minutes with the grips on maximum heat.

Then I put the bar ends back on and left the J B Weld to set for several hours.


While I was waiting, I started dismantling the spare CB250RS motor.


I found a spare sump plug and fitted a temporary washer with an o-ring, as I didn’t have any aluminium crush washers.


I started by removing the rocker covers.



Next I removed the tacho drive

Then I loosened the cylinder head cover bolts.

After removing the cylinder head cover, I removed the remaining mounting bolt for the cam chain tensioner and used a nail to lock the tabs in place. I realised at this stage that I needed a cam chain breaker before I could continue dismantling as I can’t turn the engine over to turn the cam in order remove the second mounting bolt on the cam sprocket.

I covered the top of the cylinder head with a soft cloth to keep it relatively clean until I have the right tools to continue.


I checked the heated grips the next day and found a zip tie I had forgotten to cut when I first installed them.


I cleaned out some excess J B Weld and applied some rubber grease inside the throttle housing, as the throttle had been sticking a bit. It was much smoother after that, and snapped back quicker when released than it ever had before!

Unfortunately, I was a bit rough with the heated grip when cleaning out the J B Weld, so I cracked an internal structural component on the throttle side grip and it’s a bit crooked now. I tested the heated grips and thankfully it doesn’t seem to have had any impact on their operation as they both seem to work correctly.

I’m still waiting for the replacement mirrors to arrive, and I’ve sent a message to the eBay seller. It seems they’ve disappeared between being sent by the UK Royal Mail and arriving here in Australia, and Royal Mail doesn’t provide any tracking on economy packages. I’m taking the seller up on their offer of a refund. I’ll order another set with tracked shipping later – probably from a different seller though!

Eric’s Bolt Kit

Bolt kit has arrived!


Unfortunately I misunderstood what the bolt kit was for – it’s replacements for all the engine and carburetor bolts. While these are nice quality hex key bolts, what I needed was the bolts to hold the frame (i.e. everything else) together!

Hmmm, will have to have a look into which ones can be repurposed…