Topic: CR750 style Dual oil pressure/temp gauge setup

[sazaver]

Good day Race gurus,

I want to run a dual oil gauge setup on my 750. I am interested with the Smiths or likewise gauges on cr750s





I have found this product as well and contacted with the site. They said the pressure fitting can be downsized with the adapter but the temp capillary can not be removed or shortened as it is a seal unit that is part of the gauge and it is 6ft long. Is this really the case? Not sure if there isn't a way to shorten or adjust this ?

https://www.merlinmotorsport.co.uk/p/mocal-dual-gauge-100psi-140-c-black-m-opotg

[lordmoonpie]

So if I am right, the oil temperature gauge has a small black capillary line feed from the oil gallery at the back of the barrels to the oil gauge itself. At each end there should be a screw on brass hex female screw. In the gallery that you'd screw a normal cb750 oil pressure sensor into you need a 7/8 bsp brass male to male adaptor from merlin and then the female connector on your capillary line attaches to this and then on up the oil gauge and the right connector at that end. If I recall correctly merlin supply this capillary line in a 1.5m length which is way too long for the cb750/cr750. You can shorten these by cutting the capillary line square, cutting the unwanted piece off the female hex connector which has a barbed insert into the tube. Cut all that off to leave the brass end and barb. The capillary tube is way too hard to push over this barb so what I did was get a nail that just fits the capillary tube, heat it up until hot but not glowing, insert it into the tube so it softens and slightly melts the tube and then push the fitting barb into the warm soft capillary tube. You have about 5 seconds to do this before the thermoplastic hardens again so be quick. I cut mine a little long to allow a second go on a shorter length if it went wrong but it didn't....
Worse case scenario, the capillary tube is quite cheap so you can always have another go.

[sazaver]

So if I am right, the oil temperature gauge has a small black capillary line feed from the oil gallery at the back of the barrels to the oil gauge itself. At each end there should be a screw on brass hex female screw. In the gallery that you'd screw a normal cb750 oil pressure sensor into you need a 7/8 bsp brass male to male adaptor from merlin and then the female connector on your capillary line attaches to this and then on up the oil gauge and the right connector at that end. If I recall correctly merlin supply this capillary line in a 1.5m length which is way too long for the cb750/cr750. You can shorten these by cutting the capillary line square, cutting the unwanted piece off the female hex connector which has a barbed insert into the tube. Cut all that off to leave the brass end and barb. The capillary tube is way too hard to push over this barb so what I did was get a nail that just fits the capillary tube, heat it up until hot but not glowing, insert it into the tube so it softens and slightly melts the tube and then push the fitting barb into the warm soft capillary tube. You have about 5 seconds to do this before the thermoplastic hardens again so be quick. I cut mine a little long to allow a second go on a shorter length if it went wrong but it didn't....
Worse case scenario, the capillary tube is quite cheap so you can always have another go.

Thanks for the detailed post Simon. I will look around for a shorter capillary tube just in case.. If not, I should take  merlin's.

How is the gauge on the CR750's setup on the picture? Where can I find that?

Also, I will run an oil cooler on the bike. Which would be a better place to read the temp. From the gallery or the oil coming from the oil cooler?

[lordmoonpie]

Hi Cagri, the best place to take the capillary feed from is the standard oil pressure switch point on the gallery right in the centre of the engine, under the cam chain tensioner. You can route the capillary tube up over the block under the tank, through the yokes and straight into the brass union behind the oil pressure gauge then.
Not quite sure what you mean about the gauge on the picture, it looks like a combined temp/pressure  gauge whereas the original would have been a pressure gauge alone. Merlin should do replicas of both tbh but the figment is the same, just a capillary tube and brass ferrule into the back of each.

Good luck! :-)