Loud Valve Noise Started While On Ride, Now Adjuster Spins 360

timothy.firth

timothy.firth

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Long story short I was on a ride up north in Mount Vernon and allowed rattle/ticking away started happening and then I stared dropping my right cylinder.

I made it back to Mount Vernon and did a valve adjustment in a motel parking lot, but noticed that while the intake side could be adjusted normally the exhaust valves had a tremendous amount of clearance. So much so that I could rotate the adjuster 360 degrees. Just for fun I rotated the engine 360° to the non-compression stroke and the clearances were now correct.

Now I had to get home so I carefully made my way back to the shop - on the way the valve noise remained and the cylinder would occasionally drop for a while then come roaring back. I thought for a second that the cylinder issue might be a fuel flow problem so I stopped by the hardware store on the way back and got rid of my in-line fuel filters to improve flow. That seemed to help tremendously for a few miles, but then it started again.

Back at the shop I've started taking things apart and the exhaust valves cant be adjusted BUT I was exercising the follower on the right cylinder and all of a sudden I could adjust the clearness and get it in spec, which makes me thing the valves are sticking for some reason?

Compression cold: L=165 R=155

Just wondering if anyone has experiences anything like this and could offer some guidance.
 
That's a strange occurrence for sure, and I've never had any 450 valve adjustment that would spin 360° in one moment yet adjust properly later. Looking at your posts, you mentioned the engine had been rebuilt by the PO so there's no telling what the problem might be. Sounds like you'll need to dig into it and see what can be seen. I'd start with pulling both valve covers to inspect the cams and go from there.
 
Was just down in the shop this morning. Tried to start from the top but the left cylinder valve adjustment is still spinning and the right is seemingly doing fine now. I'm going to take a few images / videos before I take the head off because I honestly don't feel confident in my assessment of the cam/follower conditions and maybe someone will see something obvious.

Also, I dont recall revving the engine up but perhaps some valve float occurred and the valves got bent while tooling around those farm roads? Or perhaps the cam chain skipped a tooth somehow.
 
Pictures/videos always help, though in this situation some of it might not be visible until teardown.
timothy.firth said:
Also, I dont recall revving the engine up but perhaps some valve float occurred and the valves got bent while tooling around those farm roads? Or perhaps the cam chain skipped a tooth somehow.
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If it jumped a tooth it probably would have bent valves, and if it did bend valves at all it wouldn't have those compression numbers.
 
Make sure you're on TDC on the compression stroke - both cam followers should feel "loose".
 
Its been a minute but just wanted to say that I found a solution to one issue and I believe a cause of the other.

The intermittent cylinder dropping ending up being the Charlies Place electronic ignition that was pre installed on the bike. When the bike got hot the EI would either stop firing or misfire. It took a lot of trial and error to figure out what was going on, as I was stuck on the idea that it was a carb issue. In the end, and after more hours on the side of the road than I'm willing to admit to, it's all fixed up and it hasn't skipped a beat since.

The loose left exhaust follower is dished. I borrowed a little video scope and was able to get a look at the profile. Not pretty.
I'm going to have to take apart the top end and I think I'll just get all the follower(s) resurfaces in Tacoma WA. Starting to wondering if I can upgrade the oil pump and get more flow to the top end so Im not doing again in a year.

Pic: where I spend all my evenings

IMG_7783.jpeg
 
Thanks for coming back to update us, and good to hear the ignition issue is fixed (adage around here, "90% of carb problems are electrical"). :)
timothy.firth said:
The loose left exhaust follower is dished. I borrowed a little video scope and was able to get a look at the profile. Not pretty.
I'm going to have to take apart the top end and I think I'll just get all the follower(s) resurfaces in Tacoma WA. Starting to wondering if I can upgrade the oil pump and get more flow to the top end so Im not doing again in a year.
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A gentle, idle-speed warmup will eliminate most if not all excess wear on your followers, even with the stock oil pump. I've been doing it for years with mine, and the left exhaust is always the first to get worn since it's the furthest from oil flow. If you're not aware, it takes 1 to 2 full minutes at idle for oil flow to reach the top end, fill the hollow camshafts and feed the lobes and followers from the orifices in the cam lobes. If you don't wait that long before riding away or revving it, that's when the oil film left from the last run will get burned through before oil flow from the pump gets there. Not sure if I've shared it with you previously, but Honda even warned about it in the owner's manual.

Important DOHC 450 and 500T warmup information

I have often mentioned the safe approach to warm-up on a 450 or 500T with respect to oil pressure to the top end of the engine when cold. The design of the cylinder head does not allow for any puddled oil to remain under the cams and followers to help keep them lubricated until the oil pressure...
www.vintagehondatwins.com www.vintagehondatwins.com

And if you do want to replace the stock oil pump with a modern gear type pump, here is that information.

Introducing A Better Oil Pump, New For 450 & 500T

This is a multi-part series on a new design oil pump for the 450 & 500T's. Stay tuned, its a fun read, gives some insight into my quirky self and ultimately reveals a new, improved and superior Oil Pump that will bolt-in to your DOHC twin! Part 1, Discovery When I first encountered the small...
www.vintagehondatwins.com www.vintagehondatwins.com
 
You bet. Love this forum. best corner of the internet.
ancientdad said:
Thanks for coming back to update us, and good to hear the ignition issue is fixed (adage around here, "90% of carb problems are electrical"). :)
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You know I've read this many times and still refused to believe it 🤔.

I am diligent about warm up, so it may be that its mostly from the previous owner, but I also checked oil flow on the front and rear right studs and while there was oil coming out of both only the front seems correct. The rear stud bolt didnt seem like it had much flow. I read somewhere that the front stud is the dominate path for oil but now I'm second guessing myself.

I'll do more research and defining going to look into the better oil pump. That looks incredible! Thanks!
 
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