Topic: Valve Job Questions....

[markreimer]

Sparky, if you're in Winnipeg (that's where I'm located too) take the head to Glen at Competition Engine. That's where I get all my stuff done. Except my 350F, which was done at Brazier Race and Machine. Both are great and very affordable


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[sparkyman]

Sparky, if you're in Winnipeg (that's where I'm located too) take the head to Glen at Competition Engine. That's where I get all my stuff done. Except my 350F, which was done at Brazier Race and Machine. Both are great and very affordable


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Thanks, I will do that. After I check out the valve seats and guides, I may get those done as well. This is a learning experience for me, so I'm doing everything I can until I get to a point where although I understand the concept, I need the help of a professional. My wife has already told me I need that help..... 

I'm trying to get the maximum learning experience and still end up with a great product in the end.

[MRieck]

I had always been told to use brass to clean things up? I've already got some brass brushes, so I'll give them a shot before buying something else.

Save your time and money, and take that head straight to a machinist. You'll never flatten it at home.

++1

[markreimer]

Totally, I hear you! Maybe my experiences will help with that:

On my 750 (my first bike, 6-7 years ago) I was burning oil, fouling plugs, bike was running like crap. I decided it must be the valves, so I tried lapping them in with stock guides. Didn't run well and still burned oil. Thanks to people on this forum, and taking a ton of photos, I learned my engine had significant blow-by, and my valve guides were out of spec.

I had Competition remove the old guides, press in new APE guides, and cut new seats, as well as mill the deck flat, and bore the cylinder block out to 2nd oversize. It's been running perfectly for a few years now. I should have done that from the start. Would have saved me the money I wasted on the first rebuild, plus the time, plus saved me a whole summer where the bike wasn't rideable due to the oil consumption problem.


I revived a '74 cb350F for my wife last year and ran into the same thing. I started by lapping valves, new rings on some spare pistons, honed the block almost up to the wear limit as it had some light scoring. I was looking to save money wherever I could.

In the end I had to do the exact same thing as the 750... Took the head to Competition and had the valve seats cut and the surface milled, but was able to keep the original valve guides after they measured in spec. The block went to Brazier (competition couldn't handle such a small bore) and bored out for bigger pistons. I'm firing it up today actually. But the bike has been out of service all summer because my budget-focused rebuild over the winter was a failure.


The next SOHC Honda I get I'll be darn tempted to just do this all off the hop if the engine isn't obviously in good running shape. The cost of parts and labour can add up, but it's nothing compared to have no running bike...

[markreimer]

FYI Brazier Machine quoted me $65 to mill my cylinder block if it measured out of spec. You'll spend more than that on oil and gaskets if you screw it up and your rebuilt engine starts pissing oil everywhere.

[sparkyman]

Totally, I hear you! Maybe my experiences will help with that:

On my 750 (my first bike, 6-7 years ago) I was burning oil, fouling plugs, bike was running like crap. I decided it must be the valves, so I tried lapping them in with stock guides. Didn't run well and still burned oil. Thanks to people on this forum, and taking a ton of photos, I learned my engine had significant blow-by, and my valve guides were out of spec.

I had Competition remove the old guides, press in new APE guides, and cut new seats, as well as mill the deck flat, and bore the cylinder block out to 2nd oversize. It's been running perfectly for a few years now. I should have done that from the start. Would have saved me the money I wasted on the first rebuild, plus the time, plus saved me a whole summer where the bike wasn't rideable due to the oil consumption problem.


I revived a '74 cb350F for my wife last year and ran into the same thing. I started by lapping valves, new rings on some spare pistons, honed the block almost up to the wear limit as it had some light scoring. I was looking to save money wherever I could.

In the end I had to do the exact same thing as the 750... Took the head to Competition and had the valve seats cut and the surface milled, but was able to keep the original valve guides after they measured in spec. The block went to Brazier (competition couldn't handle such a small bore) and bored out for bigger pistons. I'm firing it up today actually. But the bike has been out of service all summer because my budget-focused rebuild over the winter was a failure.


The next SOHC Honda I get I'll be darn tempted to just do this all off the hop if the engine isn't obviously in good running shape. The cost of parts and labour can add up, but it's nothing compared to have no running bike...

Thanks for sharing that experience with me. This is supposed to be a winter project for me, so I think I'm way ahead of schedule and I really want to be riding this in the spring. Judging by what the cylinders and pistons look like, I'm already assuming I'm getting it bored as well, but I want to do the tear down myself for the experience. Here is a picture of the carnage of sitting for 20 years 



Did you have to supply the guides, seals etc when you brought the head in?

[markreimer]

Awesome! If you need a second set of hands or anything like that, send me a message, I'm happy to help. I've been inside my 750 engine a few times now, and have a descent stockpile of spare parts too.

Are you doing the bottom end as well, or just top?

For the cylinder boring, you must bring in the pistons you plan on using, along with the piston-to-bore clearance you want. That number is usually supplied by the piston manufacturer, or in the manual. I used Cycle-X 2nd oversize pistons, which made it a true 750cc engine. In retrospect, I would have done a Cruizin Image 836 kit instead. The pistons would actually have been cheaper, and you'd get more grunt from the engine.

For the head, you'd need to supply your new guides, the valves, and the valve clearance spec. They'll press in the new guides and hone them to the right size. Then cut the valve seats. The valves will be unique to a particular guide, so make sure you don't mix them up after they've been freshened up!. You put the seals on yourself afterward.

If they do mill the gasket surfaces, be sure to have them record how much they take off. Though not common, sometimes a head is so warped that the amount they mill off can cause clearance issues with valves hitting pistons. Just a good thing to have noted.

[sparkyman]

I will be doing everything since I bought it not running and I have no idea what may be wrong with it. That was the whole challenge though, to be able to take something completely seized and in terrible shape, and turn it into something that I can ride regularly.

[sparkyman]

If you mill the head, also do the block. That way, both mating surfaces are true and flat. This will improve the gasket seal and eliminate any blow-by or oil leaks.

Do record how much material comes off both surfaces so you can calculate the final thickness of your head gasket if you change pistons/cam/valves. Not an issue if you stay fairly stock, but if you go “hot rod”you could create some valve/piston clearance issues.

On a side note, I’m not trying to harp on you about a DIY project. But the condition of your motor is going to require a professional machinist to refurbish it and make it right. You certainly can do the disassembly and assembly yourself. That’s a great lesson and very doable DIY. Another motor, you could probably “refresh”it very reliably yourself after this first one.

Great advice. Don't worry, I'm not taking anything as 'harping'. I have a lot to learn about this bike and I'm willing to listen to all sides. I will be having a professional do the machining since I do NOT want to reassemble the bike only to have it not work properly. I want a daily driver out of this eventually. From seized junk, to a great bike is the goal. 

[MRieck]

I had Competition remove the old guides, press in new APE guides, and cut new seats, as well as mill the deck flat, and bore the cylinder block out to 2nd oversize. It's been running perfectly for a few years now. I should have done that from the start. Would have saved me the money I wasted on the first rebuild, plus the time, plus saved me a whole summer where the bike wasn't rideable due to the oil consumption problem.

Sounds like you learned a valuable lesson. If funds are tight save up and be patient.

[754]

 See it gets easier if people know where you are, now you have a local guy that can help you.
You will need a couple dowels, looks like Jubba the Hut  drove his screwdriver into one.
The 4   6 mm bolts should have a screwdriver drive in the middle of the hex if you can find them, at least get them all the same.
 Is the bad piston moving in the bore ? If not we can help. If  it's deeply pitted we can get you a sleeve.

[sparkyman]

Since we are discussing milling the head and the block, along with possibly a re-bore, would it make most sense to bring everything to a shop at once? Would it help the shop make each part compliment each other better?

[754]

Yes but see if you need a sleeve first.l
If so the  re and re sleeve, then mill cylinder .
Milling same as decking or resurfacing.

[sparkyman]

Bring the head and “parts” for it together. The block and pistons/rings go together. These don’t have to be “mated”to each other, only within themselves. If that makes sense?

Sure does, thanks.

[sparkyman]

Yes but see if you need a sleeve first.l
If so the  re and re sleeve, then mill cylinder .
Milling same as decking or resurfacing.

I'll check with you knowledgeable folks for opinions first