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Discussion Starter · #1 · (Edited)
Hi everyone,

Over the past few months i've been rebuilding a CB500T motor. The process has gone really well overall. I've done a lot of cb550/650/750 motors and then a handful of the cb/cl350's but this was the first time i torn down and completely rebuilt a DOHC Honda twin.

I have my motor all the way back together but i feel a bit funny about how my intake cam marks line up and i would love the opinion of some pros and maybe some insight into the differences between the 219H & 219T cam chain.

I'll attach photos of all the timing marks, but basically what i'm working with is the exhaust cam marks will line up perfect, the LT mark on the rotor will line up perfect, but the intake cam mark is always either a notch above the timing mark on the case, or a notch below. If i position the cam where the marks are lined up then the chain wont lay down in the grooves for the master link to go through, feels as if it's a half tooth off. I have tension on the chain at my exhaust sprocket, slack on the chain at the intake where the tensioner would go, and i'm about as sure as you could be without being able to see it that the chain is properly fitted onto the bottom sprocket and is not bunched up. I spent a good few hours trying to make sure there were no combination of moves i could do in order to get the chain to line up. Everything feels good spinning over by hand, tensioner is in, valves have been set.

After this i did some research and found a lot of people on the forums that had similar problems and then even more people saying the 219H chains were no good. I didnt know there were two types of chains when i purchased mine. I guess what i'm asking here is has anyone ran a 219H chain and it been successful? Did the timing look like it does for my motor? If it's true that the only chain to run is the DID 219T i'll buy one and swap them out, but just curious what exactly the differences are?
 

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My personal preference for the DOHC 450/500 is the DID 219T cam chain, and the cheapest place to get one is Two Wheels Frank in Germany. That said, some have used the 219H chain but it can be a strange fit (as I understand it, I've never used one) because of the side plates on the chain causing the chain to ride higher in the sprockets of the cams when the rubber damper rings are in place, which are strictly for noise and are not necessary. The factory used the DID chain and that's the reason I do.

Since you're a member here now, please take a look at the link below and post an introduction for us

https://www.hondatwins.net/forums/23-member-introductions/121120-critical-read-before-posting.html
 

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I tried a 219H and could never get the cam timing notches to line up properly
Switched to a 219T and no issues at all.
 

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Discussion Starter · #4 ·
Thanks Tom! I'm pretty bad at navigating these things, i appreciate the member introduction link! I posted an introduction, really cool idea.

I think i'm just going to go with a 219T chain to be safe.

I appreciate you chiming in 76TWIN, makes it easier to buy the other chain knowing someone had the same issue and that resolved it.

Would still be interested to hear anyones thoughts/experiences with the 219H though.
 

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Hi everyone,

........... but basically what i'm working with is the exhaust cam marks will line up perfect, the LT mark on the rotor will line up perfect, but the intake cam mark is always either a notch above the timing mark on the case, or a notch below. .....

That's exactly what's happened to me more than once with the H-chains - they just don't work.
I have 4 or 5 brand new, unusable H's in a box under the bench.
 

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Discussion Starter · #6 ·
Good to know Bill! Thanks for the reply
 

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I was instructed, if the timing marks don't line up perfect to go with the advanced position. When the chain stretches they will line up again.
Just a rule of thumb.

Sent from my SM-J320V using Tapatalk
 

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Yeah, they don't always line up perfectly - the hard part is being sure it isn't a full tooth off, which might bend valves, but I agree with pattyandrick - I'd rather it be a tad advanced than retarded
 

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For what it is worth, I used a new EK 219H cam chain on a 450 this past fall because I had acquired it with a parts bike. I did not have any trouble lining up the timing marks. If I remember correctly it was a very snug fit when the master link went on and before the tensioner was installed. I also did not use any of the rubbers on the sides of the cam sprockets.
 

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There shouldn't be any difference in the crucial dimensions between the 2 chains, they're both 219 pitch, so the only way a 219 H chain would be a different fit/length than a 219T is if the plates are interfering with the correct alignment of the chain rollers and sprocket teeth.
 

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My original chain was partially off on the timing just as your pictures show. I swapped for a new 219T chain from the Two Wheels Frank link above (great guy), and everything lined up perfectly. I can't for the life of me remember if it was a 219H or just an old stretched 219T... but either way, here's another vote for going with a new 219T chain!
 

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Discussion Starter · #12 ·
Hi y'all, wanted to give a quick update. I managed to skip a tooth on the cam chain so that the line for the intake cam is slightly above the timing mark (pic attached)

After doing so i went ahead and did a leak down test & then put the motor into the frame and kicked it through for a compression test. With my left cylinder i was getting about 20% leakage and 150psi Overall everything was better than i had assumed for a rebuilt motor. The right cylinder however had about 60% leakage and then only about 60psi on the compression test. I pulled the head back off and re checked that all my valves were ok, turned out that my right intake valve was still leaking a bit. The valve seat had the slightest bit of pitting, but i was able to lap it to the point where you had to sit there for about a minute and then you could just start to see a tiny bit of gas slip past the valve. Overall looked good, and when compared to the left side the left intake actually seemed to leak just slightly in the same way.

I thought this would have cured my low compression issue, but much to my surprise when i put the head back on the right side was actually leaking worse, about 80%, still clearly coming out of the intake. I tested the left side for comparison, and it was doing worse than before as well showing about 40% leakage this time. Also sounds as if it's coming out of the intake.

What i'm trying to decide is if i need to be focusing more on my valves? Or if i actually could have a timing issue? Any advice would be greatly appreciated.

Note: When the leak down test are being done the head has been torqued to spec, cam chain tensioner installed, & valves set. I'm not exactly sure what i should be seeing leakdown wise from a fresh motor the just comparing the two tells me there is definitely something going on with my right side.
 

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Discussion Starter · #13 ·

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The timing mark I see above is often as close as you can get - it varies from engine to engine. Are you sure your valve settings are done correctly and set at the proper clearance? I leak test valves when the head is off the engine. Cam timing can affect compression, but not the seal on the valves themselves. When you put the torsion bars back in the head, did they seem to have decent preload tension on the valves?
 

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Discussion Starter · #15 ·
Hi Tom, I forgot to mention above, the torsion bar for the right intake valve measured about 73-75 inch pounds. I believe i saw someone(might have been you) say that they like to see at least 60 inch pounds on a good torsion bar. I believe my problem is more than likely the valve seat. I may try to lap the valve in a bit more, but in the instance that i do need to take the head to a shop to have new seats cut is there anything about the head using torsion bars that would cause a shop to run into problems when cutting a new valve seat?
 

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Hi Tom, I forgot to mention above, the torsion bar for the right intake valve measured about 73-75 inch pounds. I believe i saw someone(might have been you) say that they like to see at least 60 inch pounds on a good torsion bar. I believe my problem is more than likely the valve seat. I may try to lap the valve in a bit more, but in the instance that i do need to take the head to a shop to have new seats cut is there anything about the head using torsion bars that would cause a shop to run into problems when cutting a new valve seat?
How exactly did you measure that torque?
Valve extrusion is the major concern when grinding valve seats on a 450. Take too much off and you'll mess with that pre-load torque on the torsion bars, as well as the tappet adjusting range.
This really only a problem with the DOHC 450's generally.

You didn't mention the gap you used to set the tappets?????
 

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Discussion Starter · #17 ·
Hi Bill! I actually copied your idea & cut a notch out of a 3/4 socket! Now that i think of it maybe thats where i read that i wanted to see at least 60 inch pounds.

I'm also setting all of the tappet gaps at .003", i know that the factory manual calls for .0012' but i had been advised to set them at .003" because .0012" was to tight. Please correct me if that's wrong.

The more i think about it the more i feel as if the valve seat is the issue & will need cut. Without wanting to effect the preload as you mentioned do you have any advice on what to tell the machine shop? We have a pretty good local shop that i've seen do great work with sohc & dohc Hondas, but i'm not sure if it's the same process for the 450/500? Also the face of the valve it's self looks really good. I'm pretty sure there's a spec i can check to make sure it is still within tolerance, but if i do get the valve seats re cut should i look at replacing the valves as well or can i run the old ones if they're still in spec? The valve stems & valve guides all measure inspec too.

I'll grab pictures off the valve seat/valve when i take the head back off.
 

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Discussion Starter · #19 ·
Pattyandrick i've actually never done it that way but that would work fine i suppose as far as letting you know what's making contact. I've always just poured gas into the intake/exhaust and watched to make sure none leaked out past the valve.

With that being said, i pulled the head back off last night. Testing the right intake again and sure enough there is a little bit of gas still making its way past the valve if i wait a bit. I did take pictures of the valve & seat. The pitting in the seat actually looks worse in the picture than it appears in real life, which is probably why it's still leaking. At this point though i'm pretty convinced i need the seat recut.

As mentioned before i'm just a bit nervous about messing up the preload by having to much material taken off. Would it be a bad idea to have a shop cut only the seat for that valve (the only one that's leaking/pitted) just enough to get it to seal and then once it's cut measure the torque at the torsion bar to make sure it's still in spec going back together? That's where i'd notice the preload being affected correct? If theres a better option please let me know.

Sorry that this has turned into more of a thread on valve seats than it has timing chains. Should i start another thread for the valve issue or just keep it here?

I'm pretty confident if i can get this one valve sorted then the motor will go back together fine and be a good runner.

Valve seat.jpg

valve.jpg
 

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Discussion Starter · #20 ·
Here's a better close up of the pitting at the bottom of the valve seat

Screen Shot 2019-02-23 at 10.10.21 AM.jpg
 
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