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Solved VT250J SPADA cam timing and valve clearance.

Discussion in 'Maintenance' started by Kavinda, Sep 17, 2020.

  1. Kavinda

    Kavinda Member Premium Member

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    Hey all,

    Hope everyone having an amazing day, I'm a new member here and so far i'm loving the content, community and the resources i've found in here

    I'm currently restoring an old Honda VT250J Spada which was sitting in a shed for few years. I've managed to get it running by cleaning up the fuel system and carb and installing new manifolds to fix vacuum leaks it had and installed a new air filter, then the bike was running great with an amazing throttle response, acceleration and with okay idle at 1500rpm (sometimes it die at stop lights) but its old cam chains were making noises when the engine was cold so I've decided to change its cam chains hoping it would also fix the random engine stalls at traffic lights.

    What I’ve done was installed the cam chains by attaching the new chain to the old chain and feeding it trough and then I've tried setting the timing using VT250L Spada workshop manual instructions but when I turn the crank I’ve noticed the rear cylinder TDC is hitting the rear exhaust cams so I've set the timing using VTR250 service manual which instructed to set the timing at rear (T1) TDC with index marks facing down and front/rear timing marks aligned with the cylinder top.

    First I've installed the rear cam chain according to VTR manual and started the bike and the bike was running great with less noises and the idle felt lot stronger, then i’ve got overconfident and on the next day installed the front cam chain according to VTR timing and then i’ve set the valve clearance using VTR250 manual which states IN 0.17mm and EX 0.22mm cold on both cylinders but i didn't start the bike after changing the front cam chain before messing with the valves (a stupid decision i regret).

    Now when i try to start the bike it wont even try to fire up at all. VT250L Spada manual says the valve clearance is 0.15mm cold on both IN and EX which I thought makes no sense at all since usually exhaust has more valve clearance and the cam timing on that manual could’ve ruined my engine if i cranked it with the starter so i thought its information is wrong. But anyway i’ve decided to give it a shot and tried starting with both IN/EX at 0.15mm cold and still bike didn't start at all. Then I’ve revert it back to VTR specification, I've tested the sparks and both are firing fine with a strong purple/blue’ish spark, still I see no life.

    Now i'm having a hard time trying to figure out what's wrong because I don’t even know which workshop manual to use anymore and I'm doubting the information I have, can someone please help me to figure out the correct timing and valve clearance information so i can bring this little old gem back to life again.

    Sorry about the long post,
    Thank you.

    P:S some other relative information about the bike
    Jetting: pilot 35, Running 105(front), 110 (rear)
    Mixture setting: 2.00 out front, 2.25 out rear.
    Spark Plugs: NGK(R) CR7EH-9
    Cam Chains: 128L (D.I.D)
    Air Filter: A fabricated high flow foam filter
     
  2. jmw76

    jmw76 Well-Known Member Premium Member

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    As for cam timing, the Spada manual is pretty confusing.

    Use the VTR250 manual for timing info.
    There is a little drawing in the manual that shows how the cam chains go.

    cam-timing.png

    Note: All timing is referenced to the rear cylinder being at TDC.

    Check to make sure that you have not set the timing 180 degrees out when you installed the second chain.

    As for valve clearance, I would use the Spada numbers. I set mine based on these, but without using the special cam lifter tool. They are still a little noisy for my liking, but the bike runs really well.

    Peter.
     
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  3. Kavinda

    Kavinda Member Premium Member

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    Thank you, Ill recheck the timing and set the clearance to spada manual and see if it'll start.
     
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  4. Kavinda

    Kavinda Member Premium Member

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    I've finally managed to get the bike started by setting the valve timing to VTR timing and valve clearance to IN/EX 0.15mm but the bike was running to so poorly then turned out one of the intake manifold were cracked in the middle and leaking air so bike couldn't run properly, once I've replaced that It started easily and was running great.

    But as you've mentioned valves were really noisy so I've lift the cams using a screw driver and reset the valve clearance again to IN 0.15mm and EX 0.20mm because I've found this on the VT250 Spada manual.

    VT250 Spada valve clearence.jpg


    Now the bike runs smooth with no valve ticking noises and the random engine stalling has also stopped.

    However I've noticed sometimes bike backfires trough carbs when engine starts but it happens less often now, and I've noticed there's no timing marks on the spark plugs. my guess is probably because the plug is too hot since I've used CR7EH instead of CR8EH like the manual says or its the mixture, I guess I'll have to change the plugs to spec and experiment with the A/F mixture and see if there's any improvement.

    Thanks again Peter I couldn't have done it without your help.
     
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  5. jmw76

    jmw76 Well-Known Member Premium Member

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    Yes. That simple little diagram in the VTR manual makes things so much easier. The Spada manual is nothing short of confusing if not misleading.

    How does the bike sound at idle and low revs. It should be silky smooth. A carb balance might help. I just did mine by ear.
     
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  6. jmw76

    jmw76 Well-Known Member Premium Member

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    As for backfire on start, try making the idle mix a little richer. There are lots of other things that could give the backfire on startup symptom, but start with the simple simple things first.
     
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  7. Kavinda

    Kavinda Member Premium Member

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    Bike sounds much better and smoother on idles and low revs and I hear no valve noises at all except some light clicking noises coming from the bottom of the engine which it already had even before changing the timing chain and adjusting the valves, I couldn't hear that clicking noises clearly earlier because of all the loud cam chain noises it had, but now I can hear it better which starts to become an annoyance now, haven't figured out where its coming from yet or why, might have to remove the clutch cover and stator cover and see if anything is loose. I'm planning to paint the engine anyway so I'll take a look when I'm doing that. other than that bike runs great and love the throttle response.

    as you've mentioned I was trying to make the mixture little richer but then I've found out one of the choke plug was stuck open and properly not seating on the front carb, so for now changed the A/F mixture to match the choke leak till I can find a new choke cable. Its not perfect but its okay for now and backfiring also stopped once I've adjusted the mixture, rear was bit too lean and front was richer because of the choke.

    and yeah a good carb sync will do wonders, I'm still running on bench sync. I still haven't figured out how to sync by ear I don't think I have enough experience to do that haha, I'll try using the 2 bottle method.

    Also I've noticed the timing marks are back on rear, front is kinda on its way now but its running bit richer thanks to stuck choke so I guess I'll have to re tune it again once the choke issue is fixed.

    20200927_151744.png
     
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  8. jmw76

    jmw76 Well-Known Member Premium Member

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    Sync by ear is easy. Provided you can at least hear.
    Get a length of hose about 1m long. Garden hose will work.
    Remove the tank, top of air box, etc so that you can get to the intake trumpets on the carbs.
    You might need to rig up an external fuel bottle, or just run the bike in short bursts so that you do not run the fuel bowls dry during the following tests.
    Start the bike and set at a fast idle (2k rpm will do).
    Now using the tube place one end down the intake trumpet and place near the opening at the bottom of the throttle slide.
    Now listen to the hiss at the other end.
    Repeat on the other carb and then adjust the sync screw until the hiss on both carbs sounds about the same.
    Wind the the idle speed back to the stock value and check again.
    If the hiss level is the same on both carbs then you are done.
    You need to ensure you place the hose at the same location in each carb and your ear the same distance from the end of the tube.

    If you were careful with the bench sync, you should find that your carbs are very close and should not need much adjustment, if any.

    Fix you choke issue first before playing with the sync.
    One of the little plastic nuts at the carb end on my choke assembly broke off. I just repaired with some super glue and it seems to be ok for now. They do not take kindly to be removed from the carbs too often. So once you get the carbs in place, try not to remove them again.

    Have fun.

    Peter.
     
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