Hey Guys, Slowly making process on bringing my GB250 back to life. We are starting, new throttle installed, carbs cleaned, airbox refitted. Greeted with a lot of white smoke on start and smoke escaping from the engine. I have ordered most 3 Gaskets: Rocker Cover Gasket Head Gasket Cylinder Gasket I have also ordered 4 Valve Seals So I plan to remove the head and cylinder block Clean the piston / Valves and heads and reseat the valves readjust the tappets. I ran a compression test on the engine and it was running around 125PSI, when I added oil to chamber it jumped to 150PSI. I am hoping the work above will get me back up close to at least 175PSI. After a lot of searching I found that piston rings are unavailable. There is a company that provides and after market Piston and rings however the dimension (Height) and ring Height are slightly different. https://www.tkrj.co.jp/goods/m-AH1190X-13101-KL8-305.php I spoke with the company and asked if they just sold replacement rings and they said that they could sell theirs and that they should be okay to put onto the GB Piston but couldnt say 100% it would be okay. GB250 Piston Rings Spec TOP 72.0 X 1.0 X 2.7 2ＮＤ 72.0 X 1.0 X 2.9 OIL 72.0 X 2.5 X 3.0 Their Ring Spec TOP 72.0 X 1.0 X 2.8 ２ＮＤ 72.0 X 1.0 X 2.8 OIL 72.0 X 2.5 X 2.8 I have a CBX250RS Manual and that shows how to take apart, torques etc. My questions are as follows: There only seems to be a small amount of pressure added when the oil is added. Should I not worry about the piston rings just yet? In the manual there is mention of needing to use a Liquid Sealant to Crankcase meeting area, can anyone suggest to me a product for this? For the rest of the Gaskets I am assuming these go in Dry? I have watched several videos on Cleaning Valves / Piston Heads and Gasket seals (removing carbon) There seem to be lots of different ways to go about this and lot of opinion in the comments of what not to do. I have read about using Carb Cleaner / Oven Cleaner / WD40 - Brass Wire brush, Scotch Bright etc. Does anyone have any suggestions. Note I will have a better idea of what I am dealing with once I take it apart. But keen not to do something stupid in the first instance? All this can be done with the engine still in the bike or removed - Any preference, assuming removing gives you a lot better access? Hope you all dont mind all of the questions. This has been a while in the researching and I would like to get it right and the bike back on the road. I will post pics as I go.
How long has the motor sat without running?...if more than a year its possible that the oil rings are gummed up... did you test compression with heat in the motor and the carb off..have you checked the valve adjustment is correct, on these things it is tiny and a sticky valve could throw of the test.... try this mob for your rings ect http://www.bbimporters.com.au/search/myob_lookup.php?itemnumber=03.MX-09013
Thanks Wozza, it was Sat for around 1 year. I did an oil change before starting. There is a good chance as you say it rings are gummed up, I check the compression with the engine warm and the throttle fully open. I will check the Valve adjustment first. Thanks for the link.
If the engine is running fine and not blowing smoke, then I would put a bit of diesel fuel into the petrol (about 50cc per Litre of petrol) and take it for along run to get it hot (at least an hour of hard riding) and then do another compression check. If no change then a rebuild will be necessary, if better then leave alone and enjoy the bike.
Yes, try that first. The Diesel will clean any gum around the rings. The smoke may just be from oil seepage while sitting. Give it a long hard run to get every thing hot.
Could try the Threebond Super Engine Conditioner (for petrol engine) too, Repco sell it, they keep it behind the counter https://www.motatec.com.au/product.php?productid=17651
