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Discussion Starter #1
Hi all,

I started a thread having some fuel issues and I've traced that all the way back to poor compression. I measured around 90psi in each cylinder and only 110 with oil on the rings. So I'm tearing down my first bike motor. Kind of starting a thread here just to chat and ask questions. So far all I've done is take the head cover off and disassembled the rockers and lifters. I'm taking the cam out tomorrow when I get an extra set of hands to keep the motor from spinning. I'm mainly doing the rebuild as a hobby and because it's leaky. I won't be riding for another few months in Seattle anyway

So far it looks like the
*Exhaust valves have so much carbon, they may not be seating. Rocker arms have a few pits, but nothing major. I might just buy an ultrasonic cleaner and lap the valves myself if everything is in spec.
*Cam chain tensioner was stuck so the wheel is all ground up. --Can't find a replacement just yet.
*Dropped a metal spacer (see attached pics). It fell off the left side of the motor when I was pulling it out and I can't tell where it goes right away.

https://imgur.com/a/zzkTU8j
 

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Discussion Starter #3
Bottom left motor mount spacer....
Thanks. That's where I stuck it because it fit that bolt and was covered in a similar amount of old gross oil. I need to show you guys my rockers and cam when I get them out. They have a few pits, but I think I can get by without doing anything. This is just going to be a weekend hobby bike.
 

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When you are checking your valves the exhaust valves are usually ok. Intake valves on the other hand fail about 90% of the time. If there is any dishing of the valve where it contacts the seat it is no good. Valve seats also go out of round. Valve guides need to be checked as well and that is usually done by feel.

You also need to check the spring heights, my experience is most of the inner valves are under spec and half the large ones are under as well. I've gone through 20 inner springs to get 4 that are close to spec. I would expect to go through 10 to 15 of the outer springs to get 4 above spec.
 

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Discussion Starter #8
Ordered a bunch of parts today and I'm finishing the teardown when my offset 10mm comes in today. Just a few thoughts:

How is the bike running with 90psi compression when I read they won't run below 130?
How much will mufflers affect my tuning and riding? The ones on the bike are pretty roached and I'm not sure I can spend the cash right now for aftermarket or new. Common motor has aftermarket for $125+$60 shipping. Would I be better off not trying to get it all going until I can source mufflers?
 

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How is the bike running with 90psi compression when I read they won't run below 130?
It's not that they won't run at all below a certain threshold of compression, it's just that they won't run properly - lack of power, harder to start, and poor idle/won't idle
 

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If you're rebuilding the engine you have some time to worry about exhaust, I would get reproductions if you want it to run and look the best. As so keeping the engine from spinning you can put a long wrench on the rotor, turn till it hits the ground, and then the engine will be locked.

where in seattle are you located?
 

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Discussion Starter #11
If you're rebuilding the engine you have some time to worry about exhaust, I would get reproductions if you want it to run and look the best. As so keeping the engine from spinning you can put a long wrench on the rotor, turn till it hits the ground, and then the engine will be locked.

where in seattle are you located?
I'm actually up in Lynnwood. I just put Seattle because it's recognizable and I work downtown.

I've still got the stator cover on. I don't have a thin enough ratchet except my 1/4 drive that I can fit onto the cam sprocket bolt and I cant get enough leverage to break it loose so I ordered an offset 10 mm wrench. I've been taking this slow because I'm working my apartment garage.
 

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Just clamp a large pair of Vise Grips onto the cam to hold it to remove or install the cam bolts. They need to to properly torqued and I would suggest using red loctite on them as well when you get around to installing them.
 

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I had Schumman Motorworks https://www.facebook.com/Schumann-Motor-Works-1549864701915416/ do my head, they're south of Portland off 205. 503-939-7395. Not cheap but very nice work with new bronze valve guides, Viton valve guide seals, SS exhaust valves and conventional intakes.
Boring the cylinder was handled by a local speed/machine shop
When I was searching for semi-local vapor blasting I talked with these guys https://www.motoshedseattle.com/#service-restoration and they do engine builds so they'll have some recommendations I'm sure. They were very helpful to me even though they didn't know of anyone down south here. Finally did find one near me so I didn't need to go to Seattle or Grants Pass, OR.
 

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Discussion Starter #15
Alright pros. I got it apart. Check out my album and let me know what you think of the pitting on the cam and rockers. Like I said, this is just a weekend bike to mess around on for probably no more than 2-3 hours a week so it doesn't need to be pristine. I tracked down all the compression loss to two of the valves. The yellow-white one leaked carb cleaner like crazy and then the large valve on the other cylinder did the same. I know it's impossible to tell from just pics, but since two are still good...just a clean and hand lap? Is there anything wrong with me trying that and testing for leaks before letting a pro do it? I also saw a piece of thing ring metal next to one of the valve springs. I took a pic of that separately so you guys might have ideas about that.

Album link: https://imgur.com/a/i51RTyu
 

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The pits you see in the cam and rocker surfaces say they need to be repaired, call Delta.
The rings in the exhaust ports are copper sealing rings that will pop out, they're pretty stuck in there usually but you can mangle them out.
Valve? You have 2 known leaking and the other 2 may be in almost as bad condition. Until the valves are out and cleaned you can't determine if they are semi-usable. I say semi because the hard facing of the valve is only @.0002" thick and lapping goes thru that in most cases which leads to premature valve wear. I don't reuse old valves. I replace all of them and have the valve seats cut to get the proper seat width and angles. Valves guides on these engines are always suspect and may need replacement.
 

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Engines that rev to 10000 rpm don't like patch jobs and even though you aren't going to be pushing it long and hard you need to do it right.

The 2 maybe 3 of the rockers look marginal. One is no good as is. Cam has pitting on the areas of most pressure. Not a good sign.

That head/valves looks rough with lots of carbon build up and probable corrosion on the seats. Again there is no easy , cheap fix.

Based on the piston photos you are in for oversize pistons.

Give up Starbucks for a couple months and save your coins .... it's going to cost you more than you think. It will be worth it for your piece of mind and resale down the road.
 

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Discussion Starter #18
I don't have Facebook so I'm having a hard time with Schumann. What is not cheap?

I don't mind shipping these parts out if anyone has a good suggestion on who to use. I haven't measure my bore yet because I'm waiting on my degreaser.

How much is the Delta service in general? I ask because common-motor does them for $200
 

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Delta charged me $122.21 July 30, 2019 to resurface the cam and rockers
 
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