T160 Oil Pressure Opinions.

[RichardB]

My T160 was built on a budget about six years ago and at the time it could have done with a rebore, ring etc and as the crank and bearing were OK I just polished and fitted new shells, also fitted a new Hyde oil pump and clutch,

Anyway I run a pressure gauge on both the pump and crank and this year after a 10-mile run the oil pressure gradually dropped, and the worrying thing was that both gauges were reading just about zero on idle, normally the crank pressure will gradually drop, but now it's the pump as well, I was initially thinking that it was the PRV stuck but now don't think so, any ideas as to why, oil is 20w60 and oil temp gets to around 80c.

 

[sikatri]

Following conversation. Hopefully you will get some responses. Curious what is the original date of manufacture? What gauge setup are you using?

 

[RichardB]

1975 T160, the gauges are generic oil filled type one plumbed into the oil pressure switch position so reading pump pressure and one into the crank take-off so monitors the pressure drop due to bearing wear.

 

[sikatri]

1975 T160, the gauges are generic oil filled type one plumbed into the oil pressure switch position so reading pump pressure and one into the crank take-off so monitors the pressure drop due to bearing wear.

Were they installed during the last build? When did you notice the gauges acting up? Are you getting any exhaust smoke? No apparent leaks?

 

[RichardB]

Were they installed during the last build? When did you notice the gauges acting up? Are you getting any exhaust smoke? No apparent leaks?

Pretty much for the build, they gauges are good AFAICT and no reason to distrust them, no leaks, but I have always had a little smoke as it could do with a rebore or the guides are a bit sloppy.

 

[sikatri]

It would be nice to know what is the normal idle oil pressure for these engines. Actual pressure numbers would be helpful as well. Some motorcycle engines have relatively low pressure at idle and reach a high running. A quick drop would just be the first indicator that another complete rebuild is in order. So depends how fast it drops. Just don’t know specifics about your engine. I would think if it has a slow change in pressure from high to low and not instantaneous then that sounds normal. I’m sure there’s a few classic owners here that can address this better, but aside from getting accurate pressure readings, checking oil type weight, cleaning any filters in the oil system, making sure there’s no clogging and the oil flows freely and not sputtering at idle I’m not going to be able to add much. Also I’m not familiar with your gauge setup, how they are connected, as described and wondering if there’s any clear hoses involved that would allow you to see how the oil flows. The sudden changes in their readings are definitely not a good sign. Any new noise in the engine and changes you’ve noted from before? The safe bet is to rebuild, bearings do get worn. Cylinder compression test might be helpful when you’re evaluating the rebuild needs. Also it would be good to know the specs on your gauges, accuracy plus or minus pressure. Considering what you’ve noted, it is worrying, smoke and changes in pressure behavior. If it was my motorcycle I’d be doing the maintenance checks and cleaning after getting the spec pressure level information. If the range isn’t right that should help with determining the next step. Sorry I’m not really much help, except I do think there’s an issue involved, but without knowing more not sure exactly how serious. Obviously it is in need of some rebuilding if it smokes.

 

[sikatri]

BTW, please post some pictures of your gauge setup, might help others.

Here’s a rule of thumb, I found. Note it’s 10 per 1000 not as noted in title. I believe they missed a zero as the answer clarifies.

https://www.motorcycleclassics.com/...re-carbs-saving-paint-chrome-qa-zm0z21ndzols/

 

[RichardB]

I have been looking into the PRV, and it's a problem point on several engines that use similar as there are only three threads that actually seal the pressure side from the bleed side and the threads are certainly not designed for sealing up to 100psi so i and others think there is significant pressure loss especially when the oil is hot, so I am looking into obtaining a way to seal off these threads, I have several ideas and will update when I have done some testing.

 

[sikatri]

Would Teflon tape be something to look at?

 

[RichardB]

No because it's very likely to move when the PRV is screwed in and could then block the return to the sump or block the sump pickup.

 

[RichardB]

After a bit of modding of the PRV I still have near zero oil pressure at hot idle, so it's obviously down to wear in the plain mains and rod bearings dropping pressure, so it's rebuild time.

 

[sikatri]

Good luck with the rebuild. Post some progress pictures.