Valve guide replacement | GTAMotorcycle.com

Valve guide replacement

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timtune

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I'm rebuilding an SOHC 750four. I will likely be shelling out for new valves and guides. I'm wondering if the guide replacement is something I can do.

Heat it up in the BBQ ala Allan Millyard to 300 degrees and then drive them out - sounds easy.
Freeze new guides, heat up head again and drive them in with a modified old valve to ensure they go straight - sounds tougher but doable.

After which I understand they need to be reamed - I don't own tools for that job
AND then the valves need to be ground or mated to the head?

Is this more than I can chew?? Should I just get a shop to install the guides and valves?

Thoughts appreciated
 
I would check to see if the guides require replacement. should be specs available to determine if they are ok (in spec) or worn enough that they need replacement. measure up.

you may be ok with just valve seals
 
boyoboy said:
I would check to see if the guides require replacement. should be specs available to determine if they are ok (in spec) or worn enough that they need replacement. measure up.

you may be ok with just valve seals
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The last SOHC Honda CB750s were built in 1978 - that's 43 years ago.
I think OP has the right idea, do it all, do it right.
 
The old sohc valves didn't hold up to unleaded gas that well so I need a fresh set. I can't in good conscience mate new valves to old guides. Besides which the only test I know is if they "pop" when you pull out a valve with your thumb over one end.

TK4 you got a recommendation for somebody out London way?
 
timtune said:
The old sohc valves didn't hold up to unleaded gas that well so I need a fresh set. I can't in good conscience mate new valves to old guides. Besides which the only test I know is if they "pop" when you pull out a valve with your thumb over one end.

TK4 you got a recommendation for somebody out London way?
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@bitzz ?
 
Wingboy said:
@bitzz ?
Click to expand...
Not sure I'm in his good books after refusing to accept his advice regarding the use of used pistons and not putting them back in there original holes. That said I think WolfWorx would do a good job.
 
So are we all agreed that because they need to reemed after install this is not a shade tree mechanic job?
 
timtune said:
So are we all agreed that because they need to reemed after install this is not a shade tree mechanic job?
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Are you more like Alan Millyard or Bob the Builder? Some people just have the touch to make things work.
 
I do most of my own engine work, but valve guides and seats requires tools, machinery, and experience that I don't have. If I were in your position, I'd inspect the guides for proper clearance and valve seats for proper sealing and condition, and if it fails, send the whole head out valves, springs, and all to be reworked. Don't forget to keep track of which valve goes where. A valve that has been happy in a certain spot for 40 years needs to be kept happy by staying there.
 
The process is:
Heat the head, bash the old guide out (300 degrees is too hot for cast alum. 250 degrees MAX. I heat them in the oven so you can control the heat. Even heat, no hot spots)
Freeze the guide and install it, while the head is still hot, using a installation tool made for THAT guide, so you don't rivet the end of the guide (You want the tool as long as you can get. It makes it easier to get the guide in straight)
Ream the guide
Grind the valve seat: to align it with the new guide
Grind the valve: to align it with the new seat sealing surface
Lap the valve

The "installation tool" in your case is a 1/2" piece of drill rod turned down to 1/4" at one end
Reams are cheap about $25 at KBC
You can get a valve seat grinding kit online (3 angle even)

So everything but grinding the valves is doable in a shed... and i have seen people grind valves with a drill press and a bench grinder. YMMV. I rebuilt my first head, a GM inline six, at the age of 12 or 13... so there's hope for you doing this.
I will, usually, remove, install the guide and lap the valve to save coin.
The reaming and cutting the seats I farm out to Gordie Bush. I have been a customer of Gordie since 1977, so he is my only recommendation.
Gordie has a Sunnen machine that reams the guide and cuts the seat in one setup, thereby guaranteeing alignment. THIS IS IMPORTANT
IF you're going to remove and install the guide BE SURE to check with the guy that is going to do the machining BEFORE you start.
It is entirely possible to do an acceptable valve job in a shed.
To do a GOOD valve job you're going to need equipment and experience you don't got.

... not to worry. You're not going to offend me. I've met lots of hacks. When you bodge your old bike it just makes MY old bikes that much more valuable.
... and I know you're not going to BUT you should replace your 45 year old valve springs and retainers. Springs sack out with time, whether they're moving or not.
... and ethanol or unleaded fuel has ZERO effect on valve stems and guides. They eat sealing surfaces. To deal with modern fuels you would replace the valves and seats
 
The following is from the Cycle X website. They are hardcore SOHC folks. He mentions the unleaded fuel and the hammered valve tops. I'll probably be getting parts from these guys . I want to say my wallet will determine how deep I go but in fact wallet is not the problem, it's my inate cheapness.
Anyway has anyone used the highlighted technique for removing the retainers? I would think that would send springs flying all over.
Thanks for the input I'm off to the garage for a smoke and to disect another motor. Bitzz you're more than welcome to pop by for a beer and tell me all I'm doing wrong (might take two beers!) but best wait til the covids over.


The left photo shows a conventional spring compressor tool. Due to the fact we do not use the old valves because they are old technology (unleaded fuel unfriendly), the top is usually hammered and grinding the valve face is inaccurate for a couple of reasons. The valve stem is usually worn and the valve grinding chuck has a hard time finding a even place to hold on to. Also, most valve grinders in many shops are not as good as advertised. We will leave the hardness topic of the valve face after grinding to the forums and chat rooms.

Anyway, the photo on the right shows the quick and simple way to remove the valves. Take a deep well socket and place it on the top spring retainer and give it a quick, sharp tap with a hammer. The keepers, top spring retainers will pop right off.


The last photo shows a home-made tool to remove the springs with out removing the head. This tool would mainly be used by racing folks that realize springs are under severe stress and need to be changed occasionally, especially with over 200 pounds of pressure at full lift on some motors.
 
timtune said:
The following is from the Cycle X website. They are hardcore SOHC folks. He mentions the unleaded fuel and the hammered valve tops. I'll probably be getting parts from these guys . I want to say my wallet will determine how deep I go but in fact wallet is not the problem, it's my inate cheapness.
Anyway has anyone used the highlighted technique for removing the retainers? I would think that would send springs flying all over.
Thanks for the input I'm off to the garage for a smoke and to disect another motor. Bitzz you're more than welcome to pop by for a beer and tell me all I'm doing wrong (might take two beers!) but best wait til the covids over.


The left photo shows a conventional spring compressor tool. Due to the fact we do not use the old valves because they are old technology (unleaded fuel unfriendly), the top is usually hammered and grinding the valve face is inaccurate for a couple of reasons. The valve stem is usually worn and the valve grinding chuck has a hard time finding a even place to hold on to. Also, most valve grinders in many shops are not as good as advertised. We will leave the hardness topic of the valve face after grinding to the forums and chat rooms.

Anyway, the photo on the right shows the quick and simple way to remove the valves. Take a deep well socket and place it on the top spring retainer and give it a quick, sharp tap with a hammer. The keepers, top spring retainers will pop right off.


The last photo shows a home-made tool to remove the springs with out removing the head. This tool would mainly be used by racing folks that realize springs are under severe stress and need to be changed occasionally, especially with over 200 pounds of pressure at full lift on some motors.
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That's how I get retainers off. Springs are not compressed that far so I haven't launched one. Fwiw, I use a heavy deadblow hammer so that absorbs a lot of the impulse going up.
 
springs = lose things
 
timtune said:
The old sohc valves didn't hold up to unleaded gas that well so I need a fresh set. I can't in good conscience mate new valves to old guides. Besides which the only test I know is if they "pop" when you pull out a valve with your thumb over one end.

TK4 you got a recommendation for somebody out London way?
Click to expand...
Are you close to Dorchester? A friend that races in the VRRA had a few heads rebuilt by Tanner at Sibs Powersports. He said he did a good job.

He lives in Ailsa Craig so it was close.
 
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