Oil leaking from the Pacific Coast — But from where?

UPDATE: After much head-scratching and replacing several seals, I finally figured out that it was the seal around the shift lever that had gone bad.  After it was replaced, I haven’d had a single drip since.

Today when I took off the plastics I discovered what appears to be an oil leak. There were drips of oil pooled at the bottom of the water pump. Oil streaks go up the engine toward the carbs. Anyone have any idea where the oil could be coming from?


This is looking back up under the bike from the front wheel. The water pump is on the right side of the exhaust pipe. Notice the drips of oil hanging off.  The oil was changed over the summer before I bought it.  I’m pretty sure this is oil and not antifreeze.


Looking in through the left access panel by the driver foot peg.  The slave cylinder on the clutch is visible in the middle-right.  Just below it the frame is covered in oily grime.


With part of the plastics off.  Click on the picture to get a bigger version.


I’m not sure if it is coming from behind the off-white engine heat shield or not.  That will be the next thing to take off tomorrow morning when it gets light.


Another view from underneath with the plastic off.  The oil pump is in the middle.  The exhaust pipe is in the lower left corner.  There is condensation from the rain.  I have a redneck garage to work under at the moment.  Maybe someday I’ll have a real garage again…


This is the right crank case cover.  Notice the oil residue on the top of the case.


A closer look at where the oil is coming from on the right crank case.

36 Replies to “Oil leaking from the Pacific Coast — But from where?”

  1. Hi Douglas,

    Thank you for posting the detailed picture of your oil leak on your Honda Pacific Coast. Can you tell me if you you were able to determine the cause of the oil leak? I see in your Maintenance log section you have the heads off. Was this to fix the oil leak? If so how did you diagnose this as the cause of the leak? Any insight you can provide will be greatly appreciated.

    Best Regards,
    Mississauga, ON

    1. Hi Robert,

      The problem was tracked down to the cam plugs, and to a lesser extent the o-rings on the water pipes. I ended up pulling the head covers off to replace the cam plugs. In the process I managed to come up with an extra tappet shim. Didn’t bother to put it back in and so far my engine hasn’t blown up. From what I can tell, the cam plugs often leak on these bikes as the rubber gets old and brittle. Unless it’s a massive leak or you are getting tired of the oil drips on your garage floor, there isn’t a huge reason to fix them right away.

      Oh also I suspected my water pump seal might be leaking and letting oil to drip out so I replaced it while I was that far into the bike. And while I was at it I decided to replace some of the coolant hoses. In fact I’m still waiting for the last one to come in. It was on extended backorder but just shipped a few days ago.

      If you aren’t aware of it, you should check out the PC800 riders group. It’s an absolute treasure trove of info plus the people are all super helpful and friendly.

    2. Hi Douglas,
      thanks for your well documented search for the oil leak. It helps us all!
      I see that someone from Mississauga contacted you, I assume with a PC. as well.
      He is likely close to me, I wonder if you would could forward my info to him, so he could contact me if wanted.

      Bob Chamberlain
      Hm # 905-916-0133
      Cell # 416-826-3100
      Mississauga Ontario.


      Good luck with your project.

      1. Hi Bob,

        I sent your information onward to Robert.

        So far after a few hundred miles, the bike seems to be performing just fine. Ii guess that shim wasn’t all that important after all? Well, I hope not anyway 🙂

        This bike is going to be an ongoing project. I’m already thinking about driving lights, conversion to LED on the running lights, blinkers, and breaks, and a top rack/case.

  2. Hi Douglas,

    I have been trying to find an opportunity earlier this week to thank you for the very helpful information that you provided about the cam plugs.
    I spend a bit of time with the shop manual this weekend reviewing what I may be looking at. I will let you know what I find.
    Thank for passing on the contact information for Bob. I would have never known otherwise that there was a potential resource so close to me – literally in my own backyard.
    Bob, I will give you a call very soon. Thank you for offering you assistance.


    1. Hi Robert,

      Glad that the info was useful! Let me know if there’s anything I can help with from here in Oregon. One more piece of advice is to have a well-stocked fridge full of cool, refreshing beverages for when you run into a difficult PC800 challenge.

  3. Hi Douglas could you wrote me what you do to stop the oil leaking in your honda pc 800. I have the same problem with my bile as you. I will be grateful if you send this post as simple as possible becouse I dont understand all what you write hear becouse my English isin’t so good . Thank you for your attention

  4. Hi Douglas

    I have the same problem as your motor but I did not look under the engine cover / heat shield under the engine, I think these bikes from 89 years have the same problems. Could you write me what you did to your motorcycle that is not oil leaking? But when I take off my cap I write to you to ask ok becouse I have lot to do on my university ? And wher is cam plug ? Please write as simple as posible. Thank you for your answer.


  5. Hi Luk,

    There are seven places that might be leaking. They are:

    1) Cam plug (Item #7 https://www.douglasvanbossuyt.com/honda-pacific-coast-pc800-parts-list/grid-number-c2/
    2) Oil filter (Item #1 https://www.douglasvanbossuyt.com/honda-pacific-coast-pc800-parts-list/grid-number-c12/
    3) Shift lever seal (Item #14 https://www.douglasvanbossuyt.com/honda-pacific-coast-pc800-parts-list/grid-number-c9/
    4) Water pump seal (Item #19 https://www.douglasvanbossuyt.com/honda-pacific-coast-pc800-parts-list/grid-number-c9/
    5) Clutch slave cylinder seal (Item #18 https://www.douglasvanbossuyt.com/honda-pacific-coast-pc800-parts-list/grid-number-c9/
    6) Oil pressure sensor (Item #13 https://www.douglasvanbossuyt.com/honda-pacific-coast-pc800-parts-list/grid-number-d1/
    7) Air cleaner tube (Item #6 https://www.douglasvanbossuyt.com/honda-pacific-coast-pc800-parts-list/grid-number-g2/

    The shop manual https://www.douglasvanbossuyt.com/honda-pacific-coast-pc800-service-manual/ has most of the procedures.

    1) https://www.douglasvanbossuyt.com/honda-pacific-coast-pc800-service-manual/pc800-service-manual-chapter-8-cylinder-head-cylinder-piston/page-8-2/
    2) Tighten the oil filter with your hand. The oil filter can become loose over time.
    3) Pull out old seal with needle nose pliers. Put electrical tape around shift lever shaft. Use oil to lubricate inside of new seal. Gently slide new seal into place. Remove electrical tape.
    4) https://www.douglasvanbossuyt.com/honda-pacific-coast-pc800-service-manual/pc800-service-manual-chapter-6-cooling-system/page-6-3/
    5) https://www.douglasvanbossuyt.com/honda-pacific-coast-pc800-service-manual/pc800-service-manual-chapter-9-clutch-gearshift-linkage/page-9-4/
    6) All of the preparation steps to removing the water pump must be done. The oil pressure switch is next to the clutch slave cylinder and water pump. It can be removed with a wrench. Do not over tighten the new pressure switch or it will leak!
    7) https://www.douglasvanbossuyt.com/honda-pacific-coast-pc800-service-manual/pc800-service-manual-chapter-5-fuel-system/page-5-3/

    Good luck! Let me know if you have any questions.



  6. Thank you for your help and your time, I hope that soon I take all the subject on my university and then fix leaks. When I make some progress with Honda , I write to you .



  7. Hi Douglas
    I found where leaks oil. It is a place between the cylinder and head/knob . Now I don’t know what to do i wonder that should I repair this leak now or to next season becouse it is not large leakinng but it is and I should to replace seal. When i ride 100 km daily I see that leaking below the engin, could you tell me it is hard to replace that seal ? And could you tel me how to check the level of oil becouse instruction is written that I should start engin for a few minuts and turn down the engine and check the level oil after a few minutes it is corect ? becouse when i do like that I hawe olways to much oil in engin but it is depends on how long I wait when I turn down the engin when I wait 1 minute I haw smol level of oil but when I wait 3 minute I have tu much oil in engin and I don’t screw in te tester to engin when I heck the oil .

  8. Hi Luk,

    Is it leaking from the cylinder head gasket, the cylinder head cover, or the cam plug? If it is not leaking very much, you can wait until next season to repair the leak. It will take you some time to replace the seal but you can do it.

    The way that I check my oil is this: I ride my motorcycle for 10 minutes. I park the bike and put it on the center stand (so that it stands up straight). I take the dipstick out and wipe it off. I put the dip stick in the hole but I do NOT screw the dip stick in. Then I look at the measurement. The key is to only have the dipstick rest on the hole rather than thread the dipstick into the hole. Does that make sense?



  9. Do I have to check the dipstick emmediatelly when I stop the engine or do I have to wait 10 min. longer or sholter since I put the moto on the center stand what is your opinion and then oil should be between higher and lower dipstick ? I am sory that I haven’t vritten for so long but I passed them ssuccessfuly.


  10. And could you tell mi what kind of oil you use for your pc ? I know that should be oil 10w40 but it butmy question is synthetic or semisynthetic?



    1. Hi Luk,

      I put the bike on the center stand right after riding it for 10 minutes. I measure it right away. Not sure if this is right or not, but that is what I do.

      I use a 10W40 oil with NO foaming agents or detergents. Shell Rotela is a good automotive oil that many people use (it is 15W40 usually but still works). Other automotive oils will damage the clutch plates. The specific oil that I use is Hondaline Motorcycle Oil from my local Honda shop. I am not sure what you have available in Poland but any good motorcycle shop should be able to sell you the right oil. The biggest thing is to make sure that it is suitable for a wet clutch system. That means no detergents or anti-foaming additives.

      Regarding synthetic vs semi synthetic, I am not sure. Generally, I would stick with whatever the bike has already been using. When in doubt, go for real oil rather than synthetic oil.

      Cheers from Slovenia (I am on holiday)!


  11. Hi Douglas thanks for your advice and tell me do you arrived on your holiday by honda or you get on your treep normaly by airplane ? 😀

    Cheers and have a good time during holiday !


    1. I wish I could have taken my Pacific Coast with me! There are many people on fancy BMW motorcycles here. I would have looked like everyone else. 🙂



  12. So come visit Poland on the Honda we have a lot of monuments 🙂 But I still have one question, how many miles you can drive when the pile is indicated on the red band?

  13. No no I am asking about how many miles you can drive when the pile of the fuel is indicated on the red band ?



    1. Oh! Okay I understand now.

      I usually go 150 miles between fill-ups. It depends if your fuel gauge sensor has been adjusted by a previous owner or not on how many more miles you will have. I do not get worried until the needle is on the white E (well past the red line). I have pushed my PC to 200 miles between fill-ups before and know that some people have gone farther. It depends on the type and style of riding that you are doing.

      To test, you could carry an extra gallon of fuel in a fuel can and ride the bike until it runs out of fuel. You will discover that there is a lot more fuel in your bike than the gauge would indicate.



  14. Hello Douglas,
    I am not sure if you still maintain this website (I certainly hope that you do). I tried to follow your links above to the possible oil leak places and their solutions and I found out that they are no longer available. Could you provide me with updated links for this information? I am particularly interested in the Cam plug link and the shift lever seal.
    Thank you,

  15. Hi David,

    I am having an oil lead in my 1990 PC800. It is most noticeable on the front of he engine behind the radiator and spreads all over the lower engine case. The drips seem to only happen when he engine has run for a while. In is a small leak that spots under the center of the engine. I stripped off the lower silver Tupperware on the left side and tried to trace the leak to he highest point. I lose the trail behind the radiator. I have not yet removed the upper plastic (plastic is in bad shape and I hate risking more damage) so I don’t know I’d it is the valve cover

    1. Hi Craig,

      It might be coming from the cam seals. If they have never been replaced, that is where I would look. Otherwise, oil can leak from the air box as the air box boots get old. Oil gets to the air box from the crank case breather tube and is normal. I had that problem with my bike. I still have a small oil leak from somewhere that I haven’t sourced. I keep an extra quart of oil with me and feed the leak every couple thousand miles. So far, so good!



  16. I have the EXACT same leak on the right hand clutch cover side….& can’t find it You discover w h e r e it’s coming from?

    1. Hi Fred,

      I’ve never really traced down the root cause. I still get a minor leak from somewhere in the same area after rebuilding/replacing all of the oil seals around there. My working theory now is that I am getting a little leak around the oil filter and with the wind, some oil gets blown back up in under the plastics. Another possibility is that I have a leaking gasket between the heads and crank case although I haven’t been able to show that to be true. Another possibility is that the oil pressure sensor is leaking.

      As long as I watch my oil levels, the leak isn’t bad enough to cause me a problem.


  17. Helllo Douglas,

    Thanks for all this really helpful documentation. I hope you’re still checking the comments on these pages. I’m also having some oil trouble. In my case it looks like it’s from around the clutch slave (not higher up). I have a clutch slave revision set but after removing the slave saw that there’s a rubber seal around the clutch rod (lifter) that’s busted… it looks like it’s seated from behind the crank case. I can’t seem to find it anywhere in official parts lists. Do you happen to know what it is? And if so… do you know if it can be replaced without removing the whole crank case? Thanks!

    1. Hello Dolf!

      Hmm… can you send me a picture of it? I’ve rebuilt my slave cylinder before but I don’t remember seeing a gasket that is inserted from the back side of the crank case.

      Can you see the part in this diagram? https://www.douglasvanbossuyt.com/honda-pacific-coast-pc800-parts-list/grid-number-d1/

      Or can you see it on this diagram? https://www.douglasvanbossuyt.com/honda-pacific-coast-pc800-service-manual/pc800-service-manual-chapter-9-clutch-gearshift-linkage/page-9-4/

      I’m just not seeing anything that looks like it’s made of rubber in this diagram: https://www.douglasvanbossuyt.com/honda-pacific-coast-pc800-service-manual/pc800-service-manual-chapter-9-clutch-gearshift-linkage/page-9-6/

      It’s been almost a decade since I have rebuilt the clutch slave cylinder so my memory is a bit fuzzy but I think I recall that the rubber seal for the clutch rod was part of the slave cylinder assembly. Maybe it popped off your assembly and got sucked into the crank case?



  18. Thanks so much for your reply Douglas. I really appreciate it.

    Here’s a picture I took when in there: https://maquno.com/IMG_20200426_105706.jpg

    I think it might be nr 27 on the crankcase page, but it’s hard to tell. Anyway… I ordered one and will remove the clutch slave to compare it when I get it. It looks a bit like the crank case may have to come off to insert it… I really hope I can avoid that.

    1. Hi Dolf,

      In case the email I sent didn’t come through…

      That seal that you sent the picture of should come out toward you. It is installed from the outside. At least that’s what I remember from doing the job about ten years ago. I am 95% sure I replaced that seal from the outside — I never opened up the crank case so I had to have replaced it from the outside.

      Using a brass pick you should be able to get it to come out.


      Douglas in Monterey

  19. Hi Douglas… Yes it did come through, I was just busy with the bike… and kids… and life in the time of corona… I ended up removing the crank case cover because the seal at the clutch slave did have to come out inwards. The seal at the gear shifter comes out outwards. This meant I replaced the crank case seal, and the two oil seals (rings).

    Removing the (I think 30yr old) crank case seal was the biggest job… After I finally got the case free… no fun. Two days later my hands still hurt from the work haha. But I’m happy I managed the entire job with the engine in the frame… crash bars have to be removed for easier access though.

    Thank you so much for having all the documentation on here and getting back in touch. This really helps!

    So far the catch I have under the bike remains dry so I hope this was indeed it!

    1. Hi Dolf,

      That’s great that you were able to get it fixed! It’s odd that the crankcase had to come off. I must be misremembering how I did it on my bike. Or maybe there is a difference between model years. Or maybe someone installed the seal backwards in one of our bikes previously. How odd!


      Douglas in Monterey

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