Honda CB750 Sandcast
General Category => General Discussion => Topic started by: Joe K on June 23, 2014, 10:15:56 am
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I started my sandcast a couple of months ago after a complete top and bottom end rebuild. I meticulously cleaned all of the parts and assembled everything properly. I installed an oil gauge to the side of the engine. It is the non-oil type of gauge so it will continue to show oil pressure even when the engine is hot. The oil gauge showed good pressure each start-up. Then, I took my first ride and went about 22 miles. During the ride (around 17 miles) I noticed the oil gauge dropped to zero.
I purchased another oil gauge hoping the gauge broke, but when I installed it the gauge still shows zero. The needle doesn't move during idle or revving. I think I have total blockage somewhere, but I do not know where to begin. I was thinking about to start by going to the easy to get to areas first, such as the oil filter, oil tank hoses, oil pan, side covers and valve cover.
The engine oil light isn't working, so I going to fix that first. For some reason, I didn't think of it not coming on when I had the key in the ignition prior to start-up. My focus was on the oil pressure gauge.
Any thoughts will be helpful. I have done a complete rebuild on an early die-cast model before with no problems.
Thank you,
Joe K.
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when the engine's running, can you see an oil return in tank ?
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Undo a tappet cover and see if plenty of oil has been splashing about up the top end, dont run the bike until you have identified the problem, it could be pump related
pete
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Steve,
I am not sure what you mean. Are you saying do I see oil returning into the oil tank?
UK Pete,
I will open up some of the tappet covers. Good idea.
Thank you,
Joe K.
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What Pete says. Only in the spirit of being helpful, of course, make sure there is oil in tank. You might also want to remove oil pan drain plug, see what comes out, hopefully about a pint or so of oil. Then add a pint or so of oil thru tappet cap, it will run down to sump. To answer your question, when engine's running, remove cap on oil tank, shine a flashlight in opening you should see oil coming out the return. If not, then you may consider if tye return oil line collapsed, i would think unlikely. Before assuming it's something major like oil pump failure, check all the smaller details. The pump is a trochoid type, they are trouble free. Unless something has cme loose. It sounds like you had oil pressure just fine, so something happened. Either no oil, an oil supply problem or pump is not returning. Make sure both oil lines are patent.
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Sensor of the oil gauge OK? Would check if there is any signal with a multimeter.
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Excellent suggestion
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I bet its an electrical issue. Check all electric cables to the gauge.
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I bet its an electrical issue. Check all electric cables to the gauge
It is a mechanical manometer has bath of oil (as on the photo) there is no electricity it seems to me..
My opinion,
It is necessary to proceed by elimination:
Draining of the oil tank and the crankcase of pump has oil and to disconnect both hoses of the oil tank.
To remove then the oil pump, then to defuse her and to verify her completely to see if everything is good.
Then take advantage of it to blow with the air compressed both entrances of the pump on the engine (inhalation and expulsion) and make sure that the air goes out in to the hole where you connected the manometer and to the hole of the contactor of pressure.
Verify that the air takes out well in the rear 2 of the oil hoses.
Also remove the oil hoses of the engine to see if the air goes out got out of it well from both holes.
When it will have been made you will have eliminated several causes of the problem..
It is when very surprising this problem of oil pressing.. ??? ???
I do not know if I arrived has well to explain to me? ???
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Thank you very much for all of your suggestions and will go through each one of them this coming weekend. I will keep everyone posted.
Joe K.
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UPDATE - I took off the oil pan and saw that the oil pump screen was clogged with debris, such as a small cotton and hair fibers. I cannot say how that got into the engine, since I cleaned everything so well. There must have been something left behind in the oil tank, lines or who knows where I didn't see. Either way, I am happy now that I found the problem and oil pressure is back to normal.
Joe K.
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Good News!!
And did you also remove the oil tank to rinse him well with some gasoline F may well blow him with the air?
I you advice also to verify has new the screen of pump when you will have traveled good hundred miles... Very important!!
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UPDATE - I took off the oil pan and saw that the oil pump screen was clogged with debris, such as a small cotton and hair fibers. I cannot say how that got into the engine, since I cleaned everything so well. There must have been something left behind in the oil tank, lines or who knows where I didn't see. Either way, I am happy now that I found the problem and oil pressure is back to normal.
Joe K.
Joe
Was any similar material caught by the filter? Could it be filter material?
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Good reflection Wayne, it is not impossible..
Where then too much dough of waterproofness on plan of joint in the reassembly ???
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I took off the oil filter and it looked perfect. No debris at all. I then took off the oil tank and oil lines and made sure they were clean and clear of any material. Which they were clean with no debris. Finally, I lifted the valve cover and made sure there was oil in the rocker/cam area and yes there was oil with no noticeable damage. I wish Honda would have designed their frame so that you could take off the valve cover and valve head.
Now I am having an issue with some of the cylinders not firing. I removed all of the spark plugs and they looked good. I will now go through all of the wiring, especially at the coils and plugs and make sure the timing is set correctly. I don't know why I am having so many issues with this motor. I didn't have any problems when I rebuilt my early diecast a few years ago. I must have been lucky back then. This one is a challenge. But they always say that you learn the most when things are tough and challenging. I will keep you posted.
Thank you all for your advise. It helps.
Joe K.
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That's a stumper Joe. ??? The only other thing I can think of that has fibre like material is in the chain oiler gallery. Not enough to plug an oil pump screen I wouldn't think should it somehow get back inside the engine. How could it?? ???
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Boy, it seems like it would really be a good idea to know where the debris came from or what exactly it is... without knowing, would always have a concern there could be more.... someplace else in the engine ? Keep an eye on oil pressure and check for more debris ! I have electronic ignition on 2157, it's the new laser optic unit. Can't remember the brand name, i could look it up though. Points, condensors and timing are a pain in the ass. Ok once set up, but still require maintenance. For a rider, as trouble free as the CB750 is, a rider deserves electronic ignition, imho. Actually, name of ignition system is C5. I bought directly from family owned business who ditributes the C5. GREAT personal service and support,
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Joe, did you keep the debris? If yes made a photo that we can see them and also to try to understand how they were able to arrive in the circuit of oil of the engine?
Steve, as for " to improve the engine by putting an electronic ignition I agree with you, we are not any more in 1969 (Regrettably... Because have were young and beautiful!!) and it is necessary to live with his time...
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2014, nous sommes maintenant beau dans notre sagesse !
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Hum.. I see more and more effort in French from you, and soon I shall not have any more has to translate.. Very nice!!
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I made some more adjustments today. I opened my headlight bucket to see that the oil light wire came loose. I plugged it back in and crimped the connection so it wouldn't come loose again.
I didn't take a photo of the debris. The best way I can describe it is that it looked like tiny carpet fibers mixed with oil. The engine sat in my home for awhile during the rebuild, so maybe some dust and carpet accumulated in it, but again I am not sure.
Good idea, Steve to get an electronic ignition. I am really going to consider getting one. I went through all my wiring and timing today and it all seems fine. Now I am going to go through the fuel lines, carb bowls, etc. to try to find out why all the cylinders aren't firing.
I will keep everyone posted.
Joe K.
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Hum.. I see more and more effort in French from you, and soon I shall not have any more has to translate.. Very nice!!
http://www.bing.com/translator/ (http://www.bing.com/translator/)