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Discussion Starter · #1 ·
I'm posting mainly to meet my "newbie 3 post requirement" because I'd like to reply to some other posts but can't.

Anyway, does anyone have recommendations on adjusting valves on a 83 VT500C? I have no low end power so I'm thinking it could be valves out of adjustment. Carbs were professionally adjusted a couple years ago when I got the bike back on the road. Anyone have experience on other power stealers I should look for?

I'll search other forums, but as I said, I need to meet my 3 post minimum.
 

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Valves out can manifest itself as noise, lousy performance, dropping mpg or all of the above but you didn't mention mpg. Consider running Sea Foam thru the carb. Spike the gas, run the bike to get it into the system and try again after it sits a day or two. Also, your carbs may have gone out of adjustment, nothing stays fixed forever.
 

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So you cant search unless you've posted 3 times?? Thats ridiculous...


Anyway, Yes bad valve adjustment can cause that, If your suspecting valve adjustment than I imagine you've never done it to this bike, so stop riding and get at it.

If your loosing power from a bad valve adjustment than your likely not far away from ruining your exhaust valves.

As said before, your carbs being rebuilt a couple years ago means very little. Dont rule them out either. But first, do your proper scheduled maintenance and adjust your valves.
 

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Discussion Starter · #4 ·
Thanks for the advice. I'll check the carbs.
I'll also buy some feeler gauges this weekend so I can check the valves.

I found the shop manual online here and it is much better than the Chilton's manual i got with the bike.
 

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Discussion Starter · #5 ·
Arrgh, Help. Valve adjustment gone wrong?

I followed the valve adjustment instructions in the Honda Service manual, but when I got everything back together, there was loud ticking from the engine. I took everything apart and repeated the process at least 5 times. Before the maintenace, my bike was running and sounded fine. I just had a lack of power on the low end (wanting to stall in 1st gear and lurching). When I checked my manual, I knew this maintenace had not been done in years.



Here is my step-by-step, please tell me if you see anything wrong. This is on a 1983 VT500C.
  • Open timing cap and turn shaft clockwise to align line next to FT with index at bottom of view hole. I attached a photo to make sure I'm correctly aligning the marks.
  • Opened Intake valve cover on the front cylinder (it was late in the process before I finally saw in the manual that there are also exhaust valve covers).
  • Checked gap with 0.004-0.006" feeler gauge (I bought the "Go-no-go" feelers that have a range listed)
  • No gap between adjuster screw and valve stem on either intake valve. I loosened the nut, backed out the adjuster and set the gap of I could get the 0.004-0.006 feeler in, but not the 0.005-0.007 feeler. I did this to both intake valves.
  • Turned shaft to align the line next to RT with the index.
  • Checked intake valves on rear cylinder. Found them with no gap as well. Had to back out adjuster screws "a lot".
I put everything back together and was pretty proud of myself for figuring out the adjustment process. But, when I started the bike there was loud tinging in the engine. I think from both front and back.

As stated above, I readjusted following the same steps at least 5 times. When readjusting, I found the gap a little too tight or a little too loose. Occasionally, I did not have to adjust one of the intake valves.



Here are a couple observations and comments that may allow you more experienced guys to steer me right:
  • I noticed that when I turn the crankshaft past the F||, to F| mark, the rocker arms start their downward motion to the valve shaft. When I get to the |FT mark the rocker arms have moved down a bit. It seems to me that any slight difference in my aligmnent of the FT mark with the index would produce a different gap.
  • The manual indicates that I need to make sure the piston is at TDC. How do I do that other than to align the FT mark with the index?
  • I checked my Clymer service manual when having trouble and saw the photo for the ehaust valves. So I had only been adjusting the Intake valves. I opened the front exhaust valve cover and noticed the valve it stayed tight with no gap. Would the bike start making noise if I correctly adjusted the intake valves but left the exhaust valve with no gap?
Please let me know where I've gone wrong.
 

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When I adjust the valves on my bike, after aligning the timing mark on the flywheel, I always check the rocker arm assembly on the cylinder that's being adjusted. If there is slight movement up and down, then I go ahead and check the valve clearances and adjust if needed. This is how you tell if the cylinder is at TDC. If the rocker assembly is tight, then I rotate the flywheel another 360 degrees and recheck that rocker assembly. It should now be loose and ready to adjust. After adjustment on that cylinder, you rotate the crank another 360 degrees, line up the timing mark, and now the other cylinder should be at TDC.
I'm not familiar with your particular bike, but on mine you adjust both the intake and exhaust valves on each cylinder when that cylinder is at TDC, so I do one cylinder at a time.
Hope this helps!
 

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I'd say you weren't on top dead centre on the compression stroke when you did your adjustments.

The FT and RT passes by twice for each cycle, so you have to make sure that your on the compression stroke of the cycle when you stop on the FT or RT (depending on which cylinder your adjusting)

.004 is the spec, I don't like the sound of your feeler gauges? Are they not as precise as they should be?

When you do the front cylinder and line it up with the FT, all three of the valves in the front cylinder should have gap if your in the compression stroke. This means that all three valves (intake and exhaust) are closed.

Another way to check is to pull one of the spark plugs and put your thumb over the hole. When it creates pressure on your thumb its on its way up on the compression stroke.

Now if you did make major adjustments this may be a bit harder to find the compression stroke, but you can do this if your having trouble.

Open all the caps on the top of the front cylinder. Turn the crankshaft until you see that all three rockers are rotating upwards somewhat. Check to see that the FT is coming into view, Adjust all your valves to .004.

Rotate the crankshaft from that position clockwise til you hit the RT. this should than be the compression stroke TDC position and do the same adjustment.
 

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Discussion Starter · #8 ·
Thanks guys. I should have known better. I think I adjusted without being on the compression cycle. I did not think about 1 cycle for compression another for exhaust. I'm sure that will do it. I won't know for sure until next weekend since I'm traveling for work this week.

Still Bluenoser - since you have the same bike, I need to ask; Can you get to the exhaust valve without removing the radiator? I was having trouble getting a good angle for the feeler gauge. I can't imagine getting fingers or pliers in there to hold the adjuster tappet.
 

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Depends on the feeler gauges. I cant afford a nice set of snapoff feelers that are bent to fit in tight spaces, I got a cheap set and bent one myself that fits in nicely. Its possible, but a PITA
 

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Discussion Starter · #10 ·
Success

You guys were right. I was not consistently on the compression cycle at TDC. I was able to adjust valves today and the bike sounds great. My bike has much less hesitation (lack of power) at the low end.

I'll try syncing the carbs next.
 
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