1980 CX500 R café racer build project
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Thread: 1980 CX500 R café racer build project

  1. #1
    Senior Member big1000's Avatar
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    1980 CX500 R café racer build project

    Hi cx500,

    I've been putting off making this build thread for long enough. I've wanted to do a CX500 café racer for a while now, so when one popped up on my home forum I bought it. the bike runs, seemingly well (I don't have much experience with older bikes), but needs some work. eventually I plan on swapping triumph street triple R forks onto the bike, along with a mono shock in the rear (I have my eye on the 2013+ stock triumph daytona ohlins TTX, which can be had for around 300$). My main motivation for going with the Triumph forks was that I can run clip ons OR pro-taper bars. And, I got a smokin deal on the forks . For whatever reason, CBR600/1000 forks seem to be the more expensive forks to buy on eBay.

    link to my fork discussion here: http://cx500forum.com/forum/cx-custo...noshock-2.html

    The frame will need to get cut, as I really want to open up the rear to showcase the drive shaft, and monoshock. I will need to stiffen the swingarm and fabricate the mount for which ever adjustable rear shock I choose to go with. I plan on powder coating the frame, probably black. I want to do a custom stainless exhaust, which I plan on Tig welding by hand. Maybe I'll do a solid works model or something to help me determine the type and quantity of stainless mandrel bends to purchase. (found https://www.amazon.com/Stainless-Ste...drel+bend+1.75 on amazon)

    But, before I get to do all of the glorious fab work, I really want to dig into this engine to see what I've got. At first, I thought the engine had been gone through (rebuilt?) because it was painted. After further poking around with a bright LED flashlight, or iPhone as some call it, I found that the engine was probably painted while still on the bike! So I really have no idea what to expect when I go in there. time will tell. If anyone has any pointers on helping this engine sparkle, please let me know.

    Where I'm at with the engine cleaning:

    -just finished building new work bench in the garage
    -bought some Jasco paint stripper for the paint
    -researched soda blasting (I've heard this hand held gun works quite well: Speed Blaster Sandblast)
    -researched ultrasonic cleaning tanks (they have a 10L tank on amazon HERE)

    I'm really leaning towards getting the handheld soda blaster and using the Jasco stripper for the paint. The ultrasonic cleaners are pretty cheap and cool, but I'm just not sure how well the amazon ones will work. I've even considered buying a couple ultrasonic transducers like THESE, and epoxying them to a large aluminum stock pot and hooking up to a special ultrasonic power board as a kind of large DIY ultrasonic cleaner, but I may be over thinking this. Any help or ideas are welcomed.


    As for engine rebuild parts I'm considering buying, there are full gasket kits on eBay, and not sure where else. any recommendations here would be of great help. There is also a set of stainless allen head bolts which seems pretty cool, would that be a bad idea? I do like the look of the allen heads: http://www.ebay.com/itm/HONDA-1978-8...FUMrUy&vxp=mtr.

    other questions:

    -can the head bolts be re-used on these engines?
    -head gasket recommendations?


    Carbs- I've seen some people with small custom metal intakes instead of weird rubber thing thats on there, and I'm hoping to learn more about that as well. I've also heard of Murray's carbs and I'd be interested in doing that but I have no idea what they cost. Is it something where you send yours in and he rebuilds them? or are they brand new?


    Here's a few pictures of the ol' girl:








    The new 2014 Triumph street triple R forks:









    Triumph bearing kit numbers at Allballsracing.com




    New work bench bonus:

    Last edited by big1000; 08-28-2016 at 01:05 PM.
    Malinwah and Raketemensch like this.

  2. #2
    Senior Member big1000's Avatar
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    Took the CX for a little cruise for the first time today. It runs pretty well, which is why I thought it would be a good start for a project bike in the first place. I'm even more excited to tear the engine apart now and give it some love!

    A few things I noticed:

    1. The CX500 is a fun little bike to ride! Coming from riding late model street bikes, I didn't have high expectations, but knowing that the bike isn't running at its peak I'm excited about it. Putting murray's carbs on these must make them a total blast.

    2. In 4th/ 5th gear if I get over a certain rpm (don't know what rpm bc theres no tach, 5-6k maybe?) and punch the throttle the bike boggs down. I think that this may be from a low end jet that is clogged? if I accelerate very lightly from 65-70 thats about as fast as it'll go. but up until that point I don't notice it bogging down. hopefully its just a carb issue.

    3. no knocks or strange sounds from the engine

    4. Steering bearings are worn out and the forks shake a little bit. This shouldn't be a problem because I'm replacing the forks with new bearings from allballs, but hopefully the races aren't gouged out because I believe the allballs kits use the stock CX races.

    5. A friend of mine who rode behind me for a little bit said it smoked a little bit when I got on it? he said he didn't know what color it was, and it may have only been coming out one side. I'm not too sure what to make of this, hopefully its not oil getting past the rings, I was hoping to not have to replace the piston rings (maybe I should?).

    6. noticed a tiny little drip of coolant on the rear swingarm. coolant level seems fine, but I will have to verify.

    7. there is a wiring harness coming from under the tank to the right side of the forks that seems to be wet with some fluid. not really sure where the fluid is coming from because I don't see a drip from the brake fluid resevoir. The forks have schraeder valves on top and one is a little moist on the right hand side. Maybe the fluid is coming from that? there isn't an obvious leak, but the electrical tape around the harness is coming apart and not sticky anymore because of the unknown fluid.

  3. #3
    Senior Member big1000's Avatar
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    I popped the spark plugs out to see what they look like. the plugs look pretty new, but I did notice one was definitely darker than the other.



    I did a compression test with my cheap harbor freight compression tester and measured 90 psi on each cylinder... they were exactly the same, which is good, but those numbers are low. I'm not going to panic yet because the compression tester is cheap, and I don't know if it reads accurately.

    Right cylinder:





    Left cylinder:



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  5. #4
    OCR
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    Test done with both plugs out and throttle held wide open?
    You should get at least 150 or so on both sides.
    As to the bog, you should do a stator test, particularly the 5/9 wires as that is the high speed coil.
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    Senior Member big1000's Avatar
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    Quote Originally Posted by OCR View Post
    Test done with both plugs out and throttle held wide open?
    You should get at least 150 or so on both sides.
    As to the bog, you should do a stator test, particularly the 5/9 wires as that is the high speed coil.
    Unfortunately, yes. I can try to test the guage against a different gauge in my shop. Could the engine run right if it was only 90 psi? If the engine is really only getting 90psi, could it just be rings or a valve adjustment potentially?

    Im not familiar with the stator test, but i can look into it. Thank you!

  7. #6
    OCR
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    Check the WIKI for the procedure on stator testing.
    These can run on low compression but performance will suffer greatly.
    For the most part, I have found that the cheaper gauges will not read correctly. (Usually read very low)
    A leak down test will tell you where the real issue is.

    Another thing you can do is to pour a tbl spoon of oil into each cylinder and test again.
    Compression numbers should come up significantly if the rings are the problem.
    You will also get low readings from an engine that has sat unused for extended periods and will see the #s rise after being run a while and the rings free up.
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  8. #7
    Senior Member big1000's Avatar
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    Quote Originally Posted by OCR View Post
    Check the WIKI for the procedure on stator testing.
    These can run on low compression but performance will suffer greatly.
    For the most part, I have found that the cheaper gauges will not read correctly. (Usually read very low)
    A leak down test will tell you where the real issue is.

    Another thing you can do is to pour a tbl spoon of oil into each cylinder and test again.
    Compression numbers should come up significantly if the rings are the problem.
    You will also get low readings from an engine that has sat unused for extended periods and will see the #s rise after being run a while and the rings free up.
    Quote Originally Posted by OCR View Post
    Check the WIKI for the procedure on stator testing.
    These can run on low compression but performance will suffer greatly.
    For the most part, I have found that the cheaper gauges will not read correctly. (Usually read very low)
    A leak down test will tell you where the real issue is.

    Another thing you can do is to pour a tbl spoon of oil into each cylinder and test again.
    Compression numbers should come up significantly if the rings are the problem.
    You will also get low readings from an engine that has sat unused for extended periods and will see the #s rise after being run a while and the rings free up.
    I dont have the stuff to do a leak down test, but it may be good to do that before I tear the engine apart, no? I can try the oil trick, and see if I can get some direction from that.

    I plugged my compression test gauge into my air compressor and it did read about 10psi low, but that doesnt account for the other 50psi difference. 90 is pretty damn low... Maybe I should check the valves before I take the engine apart.

    I checked out the wiki, and theres a ton of good info there. I sure wish getting new seals and gaskets for these bikes was as easy as buying a set off ebay. Unfortunately a lot of people are saying to stay away from those kits. Murray said the head gaskets are junk, and to buy oem. Im wondering if I could just buy the head gasket and case seal (the .008-.010 critical thickness one, and then get the rest of the seals on ebay... That would sure be easier.

  9. #8
    OCR
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  10. #9
    Senior Member big1000's Avatar
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    Excellent resource. Looks like I could easily spend 500$ on new seals and gaskets through partzilla. I guess i'll know more of what i need once I crack the engine open. ...

    I checked the oil today- yes I did a compression test before checking the oil, haha, and the bike seems to be overfilled. I checked the level with the bike up on the stand, and the level was about 1 cm above the hash marks on the dipstick. I dont know much about these bikes yet so I dont know if the dipstick is OEM, but this could explain why my buddy saw some smoke coming out of the tailpipe on our little ride yesterday.

    Also, i found a front wherl from a 2010 triumph daytona with calipers and a tire! Pretty stoked. These are usually around 400$ and ai got it for much less. I'll post pics when it comes in.

  11. #10
    Senior Member big1000's Avatar
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    happy saturday folks!

    So I got my new feeler gauges in yesterday, and was able to do a valve check this morning. If you haven't read the above posts, my motivation in checking the valve clearances is the super low compression readings I got last weekend (90psi on each cylinder).

    Some excellent information on adjustment of CX500 valves can be found at the following sites:

    CXGLTappets

    https://motofaction.org/motorcycles/...cx500-part-01/

    Soo, after checking the valves I found that they are spot on. There wasn't even one valve that I thought was worth adjusting. I used the .100 mm for intake, and a .130 for exhaust (a little big, spec says use .120 but I didn't have it). The intakes were all spot on and the exhaust valves were slightly tight for the .130mm gauge, so I determined they were probably right at .120mm.

    Now, since the valves were spot on, the only thing I could think to do was the "drop some oil in the cylinders" trick, to see if my compression numbers went up. I dropped about a teaspoon of oil in each cylinder and re-did the compression test. The test results were as follows:

    Left Cylinder

    Before oil added: 91 psi
    after oil added: 105 psi

    Right Cylinder

    Before oil added: 91 psi
    after oil added: 104 psi

    I'm going to start tearing into the engine at this point. From what I hear the bump in numbers may point to the rings needing to be replaced. Up until now I have NOT FOUND a recommended place to purchase rings for the CX500. Please let me know if you have found a reliable supplier.

    Any pointers for the engine disassembly are welcomed. I'm thinking it may be easier to remove the head bolts from the valves while the engine is still on the bike. other than that I'm just going to go for it (watched a few youtube vids).

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