Project Bens GSX250 Cafe Project

Dude, nice. We will be two standout 250's

 

Hi Mael,

Yeah, I got the quote though, and the CR Specials jetted for a GPZ250 (closest available) and the twin throttle cable system comes to $980 with shipping

I can afford that, but i don't want to right now. That adds 25% of the total cost to the build straight away

Decisions.

 

I've got good news.

Firstly, I've found 2 sets of the original piston rings for $60 total. That means I'll have 1 spare set or I can put both in, seeing they are discontinued. Seeing that my cylinders had nice even walls i'm confident that will fix the Positive Crankcase Pressure and end the oil leak saga on the left cylinder.

Secondly, the wife and I have agreed, if the airbox from Grey doesn't get the bike running smoothly/safely (in which case I would make a custom one around the pods out of a nice aluminium, and ship his back) then I can go ahead and buy these Keihin CR Specials and put them on the bike.

So over the next (license-less) month I'll post exact videos and pictures of the installation for you guys

I wonder if I can get the heads off the bike without taking the engine out of the frame?

 

So drop sheet is down and engine is on the floor. Rhys is coming over to check my work tomorrow morning as I pull it apart. Gaskets arrived from Japan a week early (bless them) and I have some more precision measuring tools and a borrowed torque wrench so I can check my loads once I've replaced the piston rings. I have a good hope that this will sort out my issue. Hopefully this is the last time the engine is out of the frame for a few years/thousand's of kilometres.

 

After cracking the bolts and pulling off the cams and tensioner I've started running through the service manual checklist for clearances and seals.

1. PCV valve was seated loosely in its port, this is now seated correctly. Valve is clear (photos)
2. When valves seated, petrol poured into cylinder does not leak through. Might check seating manually just in case it is under pressure
3. Piston rings have a visible knurled wear on the rim, probably a good thing I am replacing them

I'll report more on progress tomorrow after I measure piston vs. cylinder diameters, ring clearances, valve clearances and wear, cam wear and timing chain wear. Any parts I will order and replace

 

Thanks Mael, thats really handy to know. That must mean that it was my piston rings. About to do all the testing on the measurements now, have a compression tester and feeler gauge this time

 

I've taken my engine to an engine specialist who has measured the diameter of the cylinder and confirmed that it has very little wear and has honed the cylinders for me. He has also shaved the head surface, de-carboned the valves and replaced valve seals and machined the valves so they seat 100%. He has also checked the spring tensions and is going to help me ensure the piston rings are correctly fitted and run in.

I ordered 2x Keihin CR smoothbore carburettors with a 250cc jetting kit, a push-pull cable throttle assembly and some grips.

My engine should now not only seal completely, but should run optimum compression, and be able to get extra squirt from the expensive mechanical carburettors i've purchased

This is going to get rather interesting. I'm in uncharted waters for sure.

 

The valves looked pretty average, I scrubbed the piston tops with a brush to de-carbon them, and the engine specialist has lapped and re-sealed the valves now. Yes there was an oil leak up through the left cylinder, but i'm not sure on riding consumption. I know that it wasn't blowing much smoke, doesn't mean it wasn't coming out in other spots though.

Surfaces have been honed and cylinder report was in his words "perfect, very little wear and dead straight"

PRETTY!!!!