Oil line check valve problem on GT250b

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rattly250b
Posts: 3
Joined: Sat Mar 31, 2018 12:07 pm

Oil line check valve problem on GT250b

Post by rattly250b »

Hello all,
Can anyone be of help regarding oil line check valves?
When I first got my 78 250b a few years ago I had problems with air bubbles in the oil lines to the LH cylinder which I finally cured by shelling out for an NOS pipe assembly. All has been well since then with the bike covering around 1000 miles a year and consuming a steady amount of 2T.
A couple of weeks ago out of the blue, I noticed that the oil line feeding the intake on the LH cylinder was empty right back to the pump but the pipe to the main bearing was still full back to where the pipe divides.
I always check the pipes after every ride just to make sure no air bubbles have developed as my previous experience has left me a little paranoid, so I knew that the pipe had emptied in the week since my previous ride.
I re-primed the pipe and took the bike out covering 40+ miles after which the pipe was still full of oil. 2 days later and the pipe had emptied again. This cycle has repeated 3 times now but the bike is running well and sounds sweet so there seem to be no problems with oil delivery, just oil draining out of this one line. I assume that the check valve on this branch is not closing fully which is allowing the oil to drain down into the crankcase (unless any of you know different)
Anyone else experienced this and if so, what needs doing to cure the fault?
I remember in the the past seeing sets of re-manufactured check valves for sale on ebay but can't see them listed there any more.

Any help or advice would be greatly appreciated

Regard
Paul
Bluehagon
Posts: 9
Joined: Fri Apr 24, 2020 7:53 pm

Re: Oil line check valve problem on GT250b

Post by Bluehagon »

I am just completing the restoration of my GT250C and replaced the check valves with Kawasaki equivalents which by all accounts are better. I bought these from CSML:

https://www.cmsnl.com/products/valve-ch ... 3siF4F4Ugo

Also, I have refurbished the oil pump with new seals etc and to avoid filling the crankcase with oil I also put a simple manual petrol tap in the line under the battery box.

At this stage the engine is running and I can’t find any air bubbles in the oil feed lines.
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