Topic: Rebuilding a F2/3 head

[jaguar]

Ok so a little back story first.

I had a friend that had a very clean F3 but for one reason or another the bottom end of one of the rods let go.
I have a feeling that it was run out of oil...

SOOoooo to help him and to get a larger bike for myself I wound up trading for it so its my problem now...

Trouble is that i am having a hard time finding a F2/3 engine to swap in.

So far the only thing that has come up is a $450-500 F3 engine that smokes as needs guides.
Maybe im just being to cheap for my own good but i think thats alot for a motor that needs that kind of work
But time is a factor as im sick of broken motorcycles in my shop so im starting to think about what it will take to do the guides.  also in the back of my head is the fact that even a used engine that i find might need that work done as preventive maintenance.

So whats involved in this job? cost and time wise?

[SOHC Digger]

That's a ridiculous amount of money for a take-out engine.  I bought my whole 78F bike for $400.

What the job entails, bare minimum, is complete head disassembly and replacement of the valve guides and seals.  The parts are relatively inexpensive from CycleX provided that your valves are still within spec.  You need a GOOD valve spring compressor.  The Loan-A-Junk from Autozone will not help.  Before you remove your valve guides, have the head bead blasted or soda blasted to remove carbon around the guides to avoid damaging the head during removal.

I removed my guides with a brass punch that was smaller in diameter than the guides to avoid mushrooming them.  To install the new ones, I placed a bronze bushing on a 1/4" bolt and lightly drove them in.  The 1/4" bolt fit nicely inside the guide and the bushing prevented damaging the bushing.

The manual gives a good description for honing your new guides, but I found the CycleX ones needed very little if any.

Now, lap your valves!!!
 

[Rigid]

A series of video instructions here:

<iframe width="420" height="315" src="

frameborder="0" allowfullscreen></iframe>

[fatmatt650]

Seems it's about time I did my F2 motor as well. Did a big tour this summer and about a third of the way in (about 20,000mi. on original motor)I started using oil at a fairly excessive rate. I'm getting some clatter under load when hillclimbing at lower RPM's and I'm told that I'm putting up a pretty decent smokescreen at times. My friends say it's obviously rings but I suspect it's the valve guide issue. Just to be on the safe side I went ahead and ordered an 836cc kit off E-bay. Anyone have any other recommendations for a reliable touring motor w/ a bit more grunt?

[jaguar]

Yeah the last 78 i bought was a compete parts bike(a cam chain failure) and it came with a title and 19/18 lesters for $200...
but lets face facts we all wheel and deal and put alot of hours into "the hunt" and hate to pay retail....

Well what are the real chances that it only needs guides and not valves too?
And why does it look like all guides are the same when it comes to "aftermarket parts"
I see APE lists guides for about $75

I thought that it was a bigger job to replace them

[SOHC Digger]

Just to be on the safe side I went ahead and ordered an 836cc kit off E-bay.

I would caution you against using the standard 836 kits in an F2 unless you are putting a different head on.  The F2's and F3's have a pretty significant dome to the pistons and, consequently the head.  The standard 836 kits, such as the Weisco kits, were designed for the 69 thru 76 engines that have VERY little dome to them.  If you use one of these kits with your F2 head, you will be sacrificing a LOT of compression!

Cycle X has an 836 kit specifically for the F2's and F3's that maintains the compression ratio.  It is a little pricey at $449, but it's the right thing to do.


Or you can go all out with this kit for $1049!!!

[Pat_at_APE]

Finally, Something I know about (as apposed to always learning from you folks)!

Replacing valve guides is not a hard job.  It's all the work you have to do to the head after that takes the time.  Honing the guides to match your valve stems and then cutting the seats to match the new guides, etc is a lot of work. 

We offer this service at APE for the F2 head for $699.00 done by Big Jay so you know it's done right.

Cheers,
Pat

[jaguar]

Finally, Something I know about (as apposed to always learning from you folks)!

Replacing valve guides is not a hard job.  It's all the work you have to do to the head after that takes the time.  Honing the guides to match your valve stems and then cutting the seats to match the new guides, etc is a lot of work. 

We offer this service at APE for the F2 head for $699.00 done by Big Jay so you know it's done right.

Cheers,
Pat

Oh...
Well if i were to order all of the parts that you would use in that job how much would it cost?


Part of me thinks that if you are replacing guides you should replace the valves themselves but another....and cheaper part of me thinks that it really doesnt matter as long as the old valves are within spec with the new guides

[SOHC Digger]

We offer this service at APE for the F2 head for $699.00 done by Big Jay so you know it's done right.

What's included at that price?!?!?

[SOHC Digger]

Part of me thinks that if you are replacing guides you should replace the valves themselves but another....and cheaper part of me thinks that it really doesnt matter as long as the old valves are within spec with the new guides

Just because the guides are worn does not mean you have to replace the valves.  That is why the guides are made of brass.  They are intended to wear so that your valve stems DON'T wear out!  The only reason to replace them is if they are worn beyond specs or you want performance valves (like in the kit above).

[fatmatt650]

Just to be on the safe side I went ahead and ordered an 836cc kit off E-bay.

I would caution you against using the standard 836 kits in an F2 unless you are putting a different head on.  The F2's and F3's have a pretty significant dome to the pistons and, consequently the head.  The standard 836 kits, such as the Weisco kits, were designed for the 69 thru 76 engines that have VERY little dome to them.  If you use one of these kits with your F2 head, you will be sacrificing a LOT of compression!

Cycle X has an 836 kit specifically for the F2's and F3's that maintains the compression ratio.  It is a little pricey at $449, but it's the right thing to do.

-----------------------------------------------------------------------------------------------
So the $110 kit off ebay is no bueno?
http://www.ebay.com/itm/140641927323?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
Dang, I blame the Lagunitas Brewing Co. for making such an excellent product that my research capabilities are dulled while heightening my enthusiasm for late night e-bay purchases. There might be a class action lawsuit here.

[fatmatt650]

Anyone have any thoughts on replacing the head?

[fatmatt650]

Will those pistons work in my F1 motor?

[jaguar]

Those $110 kits will not work with a F2/3
I dont think that they work with the early Fs either

[fatmatt650]

Some interesting info on piston compatibility here - http://forums.sohc4.net/index.php?topic=57528.msg703826#msg703826

Bikebandit.com lists the same part # for the 76 750f pistons as for the 77 750k pistons.

Quote from: gschuld on June 05, 2011, 08:44:36 pm

    Could someone give me an idea as to what compression ratio I would end up with if I used this kit(which I just ordered ) in a 76 cb750f engine?  It doesn't seem like it would be very high.  Any idea as to how much I can reasonably increase the CR with head milling, etc?

    Thanks


They come in at about 9.5:1 compression if you do not modify the head to add a quench band. If you add the quench band, it drops to about 9.25:1, depending on how much you taper the edges of the chamber. Don't forget: you are increasing the displacement by about 14% with these pistons, while the chamber remains the same as for the 736 engine.

The Wiseco pistons, with their domes, come in at an advertised 10.5:1 at 836cc, but that number presumes an untouched chamber. It makes for a lot of extra heat and a tendency to knock at low octanes, so the lower CR of these pistons is a good bet for trouble-free riding. - Hondaman
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Okay, threadjack over, thanks for the heads up on the piston issues. I'll post further piston questions in the thread about pistons.

I may bite the bullet and send my head down to APE. It may be twice what I paid for the bike but I doubt I'll regret it after it's done.

[scottly]

A series of video instructions here:

<iframe width="420" height="315" src="

frameborder="0" allowfullscreen></iframe>

There are several errors in the video about cutting the valve seats. For example, the 45 is always the first angle cut; the 60 and 30 cuts are used to adjust the contact area on the valve face. The back and forth motion of the cutter in the video will result in a "wavy" cut on the seat, since the individual cutters are sweeping over the same areas over and over. A smooth rotation in the cutting direction would give a better sealing surface.

[Don R]

A series of video instructions here:

<iframe width="420" height="315" src="

frameborder="0" allowfullscreen></iframe>

There are several errors in the video about cutting the valve seats. For example, the 45 is always the first angle cut; the 60 and 30 cuts are used to adjust the contact area on the valve face. The back and forth motion of the cutter in the video will result in a "wavy" cut on the seat, since the individual cutters are sweeping over the same areas over and over. A smooth rotation in the cutting direction would give a better sealing surface.

Thanks, that didn't look right to me either.

[SOHC Digger]

Before you go cutting valves, do some measurements and take note of the service manual!  The service manual posts specifically what is in spec with the valves and also states that these valves CANNOT BE GROUND!  Now this may possibly have been a money-making thing for Honda, but I find it hard to follow most things in the service manual as Gospel on some things while disregarding others.

[Rigid]

A series of video instructions here:

<iframe width="420" height="315" src="

frameborder="0" allowfullscreen></iframe>

There are several errors in the video about cutting the valve seats. For example, the 45 is always the first angle cut; the 60 and 30 cuts are used to adjust the contact area on the valve face. The back and forth motion of the cutter in the video will result in a "wavy" cut on the seat, since the individual cutters are sweeping over the same areas over and over. A smooth rotation in the cutting direction would give a better sealing surface.

Having actually done this, rather than theorizing, the back and forth motion creates a smoother surface requiring less lapping.  The key is to overlap each rotation and to move the cutter each time.  A final sweep all the way around will indicate the cut is smooth if it doesn't grab or drag the cutter.  It is all in the feel and the back and forth motion is ideal.  As far as which surface to cut first, it does not matter at all, each surface is cut lightly at first and then the contact band adjusted with subsequent cuts.  It is always best to base your responses on actual results rather than just wanting to type something and seem informed.

[MRieck]

A series of video instructions here:

<iframe width="420" height="315" src="

frameborder="0" allowfullscreen></iframe>

There are several errors in the video about cutting the valve seats. For example, the 45 is always the first angle cut; the 60 and 30 cuts are used to adjust the contact area on the valve face. The back and forth motion of the cutter in the video will result in a "wavy" cut on the seat, since the individual cutters are sweeping over the same areas over and over. A smooth rotation in the cutting direction would give a better sealing surface.

Having actually done this, rather than theorizing, the back and forth motion creates a smoother surface requiring less lapping.  The key is to overlap each rotation and to move the cutter each time.  A final sweep all the way around will indicate the cut is smooth if it doesn't grab or drag the cutter.  It is all in the feel and the back and forth motion is ideal.  As far as which surface to cut first, it does not matter at all, each surface is cut lightly at first and then the contact band adjusted with subsequent cuts. It is always best to base your responses on actual results rather than just wanting to type something and seem informed.

That being said I'd recommend a Serdi over Neway, stones and/or any other hand held device. Stem heights and cut widths are very, very consistent (with the Serdi) which is very hard to achieve otherwise.

[jaguar]

anyone have a link or price list for the guides?
i keep finding guides that say 69-78 and i dont think that can be right

[niclpnut]

dynoman.net/engine/valve-guides.html

Second section for 750 SOHC bikes.  The guides are the same for all models of SOHC 750 hondas from 69-78 K and F models.

Nic

[jaguar]

dynoman.net/engine/valve-guides.html

Second section for 750 SOHC bikes.  The guides are the same for all models of SOHC 750 hondas from 69-78 K and F models.

Nic

Is that true?
see now im lost again

[Pat_at_APE]

Finally, Something I know about (as apposed to always learning from you folks)!

Replacing valve guides is not a hard job.  It's all the work you have to do to the head after that takes the time.  Honing the guides to match your valve stems and then cutting the seats to match the new guides, etc is a lot of work. 

We offer this service at APE for the F2 head for $699.00 done by Big Jay so you know it's done right.

Cheers,
Pat

Oh...
Well if i were to order all of the parts that you would use in that job how much would it cost?


Part of me thinks that if you are replacing guides you should replace the valves themselves but another....and cheaper part of me thinks that it really doesnt matter as long as the old valves are within spec with the new guides

Sorry for the slow reply... Work keep getting in the way... 

That price includes:
New SS Valves $49.95 each x 8 pcs
New Bronze Valve Guides $73.08 for the set
New Valve Stem Seals $24.87 for the set

And the labor to clean up the head, cleaning up of the ports, replace the valve guides, hone to fit the new valves, Serdi full radius seat cutting, lapping in, surfacing the head, and assembly. 

Cheers,
Pat

[jaguar]

Finally, Something I know about (as apposed to always learning from you folks)!

Replacing valve guides is not a hard job.  It's all the work you have to do to the head after that takes the time.  Honing the guides to match your valve stems and then cutting the seats to match the new guides, etc is a lot of work. 

We offer this service at APE for the F2 head for $699.00 done by Big Jay so you know it's done right.

Cheers,
Pat

Oh...
Well if i were to order all of the parts that you would use in that job how much would it cost?


Part of me thinks that if you are replacing guides you should replace the valves themselves but another....and cheaper part of me thinks that it really doesnt matter as long as the old valves are within spec with the new guides

Sorry for the slow reply... Work keep getting in the way... 

That price includes:
New SS Valves $49.95 each x 8 pcs
New Bronze Valve Guides $73.08 for the set
New Valve Stem Seals $24.87 for the set

And the labor to clean up the head, cleaning up of the ports, replace the valve guides, hone to fit the new valves, Serdi full radius seat cutting, lapping in, surfacing the head, and assembly. 

Cheers,
Pat

No worries about the time....hope you were not tracking a shipment across the states 3 times....lol

Actually thats not bad for the labor involved, here its not had to find $100 per hour shops.
so most of that price is in the actual valve cost.

thanks so much for the info its helpful to put together a picture of what im getting into






I do have the head from the blown motor but im not sure if i trust parts from the motor since it ran out of oil
SO to do just the guides is like $150 in parts....ok


Any one have ruling on chances of other things needing to be addressed while in a motor that already has bad guides?
Kind of like when i think about motors that need new pistons i just go into it knowing that the cam chain and tensoner will be bad too