750 Oil control jets.

[royhall]

Just had a horror moment reading another thread where it says "oil jets, what oil jets". Just like that engine builder, I didn't know about the oil jets either.

When I stripped the engines top end I found a problem with one of the cam carriers. The oil drilling to just one of the journals was blocked causing scoring, the other journal was okay. I replaced the carrier with a good used one, but as I didn't know the oil jets existed I didn't clean them (oops). As I say, only one side of the carrier was damaged, the other good. This probably means the oil jet was not blocked and oil was flowing, or they would both be damaged. I found the blockage in the carrier itself.

Is there an easy way to run the engine and verify oil flow, without oil blasting everywhere. Thought I may take the tank off and remove the tappet caps one at a time and see what happens. Is this a good plan, or am I stripping it again.

Cheers all.

[Bryanj]

You can run the engine with all the caps off, yes oil will spray out in small quantities but not a vast amount. back when did many re builds where the owners had done there own and not kept the oilways scupulously clean blocking a jet, also had many carriers bushed with bronze. If it was me i would take it back out, remove the cam and carriers and take the jets out to give them a thourough clean also blowing air through the oilways to ensure no gasket debris or sealant blackage

[Mike on a bike]

I don't know if you were referring to my thread but here are some pics that may help. A. is with the restrictor removed and B. is with the restrictor in place. It has an O ring around it and looks like it is part of the engine case so it is very easily missed. Just take a pointy nosed plier and pull it out. Definitely sounds like the problem you have. Unfortunately you will have to strip the top of the motor down. I had to do it twice with new gaskets each time.  One of mine was 75% blocked.

[royhall]

Thanks for that Mike. Did not realise these were removable jets when I was doing the engine (first Honda 4 for me). However, I did blast carb cleaner and compressed air through them to clean up any old oil etc. Shame they didn't blow out of the seats at the time. So am hoping I will be okay. Going to try to do a running check through the tappet covers this afternoon. Fingers crossed.

[MarkCR750]

Thanks for that Mike. Did not realise these were removable jets when I was doing the engine (first Honda 4 for me). However, I did blast carb cleaner and compressed air through them to clean up any old oil etc. Shame they didn't blow out of the seats at the time. So am hoping I will be okay. Going to try to do a running check through the tappet covers this afternoon. Fingers crossed.

Roy, how did the running check go?, I'm interested because I didn't rebuild the engine that I am currently using in my CR (I have another engine that I am boring out and rebuilding), the one that's in there seems to run ok but had been sat for years so I'm asking for trouble really by not stripping it, I did clean the strainer gauze but that was about it.

[Bryanj]

Sorry but seen so many disasters i really think its worth removing them to clean for sure, only gasket needed would be rocker box and if removed carefully that may be reusable if the engine has not run

[NigelWilmshurst]

I agree definitely remove and clean these little restrictors, also test all the little oil ways in the cam carriers, I use brake cleaner as it evaporates to loosen any oil and blow out with an air line to check every oil way is clear.

[MarkCR750]

Hmm, your right of course Bryan/Nigel, have I got the energy to take the engine out again?, I suppose it's less work than replacing the cam etc, thanks for the advice.

[Waggles]

Mark,

I have to agree that checking the jets is undoubtably the best and safest option, just to add a little balance tho I did not rebuild my F1 motor which had sat for 25 years. I reasoned that as it was very low mileage it had not been apart so hopefully all was well. I have done around 5,000 miles on it now with no problems. Risky? probably, lucky? definitely, but it is possible.

Just didn't want you to feel lonely as the only one who had risked it! 

[Bryanj]

If it hasn't had a problem and had not been apart the risk is minimal, problem with the one under discussion is that it did run a bearing and has been apart so those jets need checking

[MarkCR750]

Bryan/Waggles, thank you for offering to underwrite any damage that occurs to my engine due to not checking my oil restrictors, very generous of you !  , .....only kidding, if I do decide to take the risk (slight risk?) then it's my decision, to be honest I think I will just run it, if it goes bang it will force me to get on with the boring out and rebuild of the other engine, cheers Mark.

[Bryanj]

Mate,  your bike, your pocket, your time. Things are a lot different when you are doing it as a job!! I always look at as if I was doing it for somebody else not for me

[MarkCR750]

Agree Bryan, all the stress disappears when your doing something for yourself, if it goes wrong so what, just do it again, if it's for someone else then as you say it's a different matter, that said this build has gone well so far, no major probs (apart from when I reversed the battery terminals but we won't mention that), all I need now is a bit more rain to keep me off my road bike and I'll have time to get it finished!

[royhall]

Got chance to get in the garage this afternoon and have a look at the oil flow situation.

I warmed the engine enough so it would tick over without the choke. I then removed the No.4 exhaust tappet cap (this was the side that had the previous damage), with a torch and a pile of rags on standby. Catching the heavy flow of oil with a rag I had a quick look in. I can see a lot of oil spraying onto the cam and followers from the carriers oiling jets and oil spraying out of one of the cam journals (cant see the other one). Repeated the same on No.1 with the exact same result, and the same quantity of oil. I am now happy that I have a very healthy oil flow to the cam carriers, so am going to leave the engine well alone and get on with running it in.

Just to recap. Although I didn't know there were removable oil jets at the time, I still had the sense to clean out what I thought was an oil drilling in the head, with carb cleaner and compressed air. So it appears to have done the trick. Also, only one journal of the cam carrier was damaged and I found that blockage actually in the carrier. So the control jet was probably clean or the other journal and the cam/followers would have suffered. The damaged carrier was replaced with a good used item when I rebuilt the engine.

I think I may have just dodged a bullet. Oil control jets will now not be neglected ever again. Hopefully this thread will prevent somebody else having the same problem, and may not get as lucky as I did.

Cheers all.