Topic: 1977 F2 836cc Cam Upgrade

[B Raady]

Howdy all from OK!  Just bought a '77 F2 that has the Wiseco 836 big bore kit.  The previous owner said the cam chain needs to be replaced, new valve springs wouldn't hurt, and replace any old rubber o-rings and gaskets, etc etc.
I plan on putting a new cam chain in, but while I'm in there I figured I'd try my hand at putting in a little hotter cam to accomodate the big bore kit.  Here's what I have and intend to use:
-Kehin Carbs with pods
-4-1 Exhaust
-836 Kit; new pistons and rings were installed
I've done some reading on the forum for a cam, but I think I need a little more personal opinion.  I'd like a cam that has good mid-range and top end, yet still retains a good low end.  Megacycle's 125-30 seems to fit the description, but didn't know what you guys thought. 
Could I get an opinion on cams, valves, springs, etc.  I promise to post pics of the install if I get enough help...

[MCRider]

You do know you have to split the cases to put a cam chain in?

That would be  a good cam. But I'll let you know this. Sometimes after a big bore and a pipe, head work should be the next step.  At a speed shop I worked at in my youth, we had two buddies with virtually identical bikes. Put 835, RC pipe in both, and a cam in one.

The bike with the stock cam ran better in all ranges. The guy who bot the cam was bummed.

I think the F2 is the one with problems with the valve and the guides and premature wear?  If so, may be best to leave them alone and get a street port job on the head.

[B Raady]

Hmmm... Is splitting the case a big deal?  I planned on pulling the motor to have it painted again as it's losing the black color.  It seemed to be running strong the other day, just needed to be jetted and tuned better.

I just don't know if it's really worth it to do all this work.  Thanks for the reply, I appreciate it.  Maybe I'll just leave it alone for now and enjoy the ride for a while.  It definitely needs carb sync and tuning though, so maybe I should wait to see how she reacts to that before I go messin around in there. 

[MCRider]

Hmmm... Is splitting the case a big deal?  I planned on pulling the motor to have it painted again as it's losing the black color.  It seemed to be running strong the other day, just needed to be jetted and tuned better.

I just don't know if it's really worth it to do all this work.  Thanks for the reply, I appreciate it.  Maybe I'll just leave it alone for now and enjoy the ride for a while.  It definitely needs carb sync and tuning though, so maybe I should wait to see how she reacts to that before I go messin around in there. 

I'm pretty sure its the F2 that has the premature valve and guide wear. Somewhere around 20 to 30K miles, they need to be replaced. Good time for the cam chain then. How close are you to that?

Splitting the cases is a 8 to 10 hour job for a mechanic that knows what he's doing. X4 for us amateurs. Part of that is the engine removal and install of course. A mechanic would pull an engine in less than 45 min and reinstall in less than an hour. Its not that its hard but its the biggest job you can do and takes time. And its hard to resist the temptation to spend, spend while you're in there.

Unless you're near the 30K mark on mileage, I'd tune it, ride the p--s out of it while saving up and studying up, for the rebuild.

[simon#42]

you dont have to split the cases , it is possible to cut the old chain then use a soft link to join  the new one.  as MCrider says check  the valve guides for wear , the exhaust guides on mine where gone in 20,000 miles . if so have a look on the APE web site they sell a better quality guide which should last longer

[voxonda]

Yes, the bronze valve guides do a much better job. About another cam, think MC has a point. If the oem cam is good leave it.

Rob

[Yoshi823]

On my F2 head I replaced the valve springs with S&W items,made some aluminium/bronze valve guides,polished the ports while the old guides were out,had the OEM cam base circle ground for more lift/duration etc. But while I had the cases apart to have the crank out to have it polished/balenced/lightened together with the rods being done, I bought & installed a heavy duty cam chain & replaced with OEM parts the primary chain & tensioners for both the primary & cam chains.It ran with Yoshi 823 pistons but standard carbs, as these worked well with the modified standard cam.

[Terry in Australia]

Yeah, the F2 was the most fragile CB750, and a lot of this was caused by the poor cam design, so chucking it for something that doesn't snap the valves open and closed so hard and hence doesn't put so much strain on the cam chain wouldn't be a bad thing. Which Wiseco 836cc kit have you got, the correct (but discontinued) F2 kit, or the more common K series kit? If it's the K kit, the problem is that the K domes are much lower than the F2's, so your compression ratio will be way down. If you can post a pic with the head off we can tell you which one you have.

The best cam chain around is the Tsubaki hex plate race chain for the low low price of around 28 bucks from Z1 enterprises, and Jeff the proprieter and a member here (and a good bloke) will sell you a soft link so you can replace the chain without splitting your cases, something I wouldn't recommend, unless you need to replace a leaking seal, as the man says, "don't fix what aint broke". While you're at it, replace the cam chain tensioner assembly, once again, no need to split the cases.

I bought a 1 owner, well maintained F2 10 years ago, it had 50,000 miles on the clock and didn't display any symptoms of accellerated top end wear, maybe I was lucky, but I think it was more down to the PO looking after uit as well as he did, I should have kept it, instead I bought an absolute dog of an F2 that cost me over 5 grand to restore and as much as I try, I just can't love it! Cheers, Terry.  

[B Raady]

Wow, thanks for all the input.  Sounds to me like it'd be worth it to at least take a look inside to see how the valves look.  MCRider, I'm not sure as to how many miles this thing has because the previous owner had swapped the speedo/tach unit.  If I'd guess it'd be around 20K.

I completely agree with the "ain't broke don't fix it" motto.  There is maybe 1000 miles on this 836 kit from the previous owner and I'm not exactly sure which kit he used.  He was a Honda mechanic, but then again you never know. 

Terry, since the valves snap open and closed would it be better to replace the springs with something a little lighter to prevent excessive wear?

If I do find that the valves are about to go, what would you guys recommend replacing (other parts, brands, styles, etc.)?

[eurban]

Just to emphasize Terry's comments about which Wiesco kit you have in your bike . . .The the F2 and F3's combustion chamber is larger than the K bikes.  The K 10.25 to 1 CR kit when used in an F2/F3 will give you a CR of around 8:1. This does not yield satisfactory results.  Its been a long time since Wiseco made an F2/F3 kit and many people have no idea that there is a significant difference head design between these and the K bikes.  Basically, don't spend your money on hop up parts till you are confident that the correct big bore kit was installed!  I believe it is Dynoman that now makes a big bore kit for the F2/F3. . .

[B Raady]

Just to emphasize Terry's comments about which Wiesco kit you have in your bike . . .The the F2 and F3's combustion chamber is larger than the K bikes.  The K 10.25 to 1 CR kit when used in an F2/F3 will give you a CR of around 8:1. This does not yield satisfactory results.  Its been a long time since Wiseco made an F2/F3 kit and many people have no idea that there is a significant difference head design between these and the K bikes.  Basically, don't spend your money on hop up parts till you are confident that the correct big bore kit was installed!  I believe it is Dynoman that now makes a big bore kit for the F2/F3. . .

If I find that the Wiseco kit is for the K, is there a way to compensate for the larger chamber and get my compression back?

[bucky katt]

Just to emphasize Terry's comments about which Wiesco kit you have in your bike . . .The the F2 and F3's combustion chamber is larger than the K bikes.  The K 10.25 to 1 CR kit when used in an F2/F3 will give you a CR of around 8:1. This does not yield satisfactory results.  Its been a long time since Wiseco made an F2/F3 kit and many people have no idea that there is a significant difference head design between these and the K bikes.  Basically, don't spend your money on hop up parts till you are confident that the correct big bore kit was installed!  I believe it is Dynoman that now makes a big bore kit for the F2/F3. . .

If I find that the Wiseco kit is for the K, is there a way to compensate for the larger chamber and get my compression back?

you could mill a little material from the deck surfaces of both the head and the cylinder block but too much and you'll run into the problem that the cam chain will be too long. you could also try building up some aluminium weld then machine it but i'm not sure that would even work, it just popped into my mind as i was typing. of course you can also just get a 750k head and run the f cam in it.

[B Raady]

Just to emphasize Terry's comments about which Wiesco kit you have in your bike . . .The the F2 and F3's combustion chamber is larger than the K bikes.  The K 10.25 to 1 CR kit when used in an F2/F3 will give you a CR of around 8:1. This does not yield satisfactory results.  Its been a long time since Wiseco made an F2/F3 kit and many people have no idea that there is a significant difference head design between these and the K bikes.  Basically, don't spend your money on hop up parts till you are confident that the correct big bore kit was installed!  I believe it is Dynoman that now makes a big bore kit for the F2/F3. . .

If I find that the Wiseco kit is for the K, is there a way to compensate for the larger chamber and get my compression back?

you could mill a little material from the deck surfaces of both the head and the cylinder block but too much and you'll run into the problem that the cam chain will be too long. you could also try building up some aluminium weld then machine it but i'm not sure that would even work, it just popped into my mind as i was typing. of course you can also just get a 750k head and run the f cam in it.

Good grief.... I don't know that I am that confident to do this kind of work to get that compression back.  Bucky Katt, what do you think of the valve situation.  Should the springs and guides be changed out to something a little softer and lighter? 

[bucky katt]

if it were mine, i'd go with new guides (the 77-78 750f are notorious for going through guides) measure the valve stem diameter in several spots (and every 90 degrees around the stem to see if it's out of round) if youre going to a hotter cam then you should really get new springs and titanium retainers as well. do it all now, while it's apart.

[voxonda]

In Holland back then most new F2 where dismantled on top to put in new guides under warranty. Honda did a bad thing to the unbreakable rep of the CB 750.

[Terry in Australia]

Yeah, all of the above info is good mate, but don't panic, it aint the enf of the world. I've had all sorts of fun and games with my F2 resto and now I've settled on replacing the top end (cylinder block and head) from a K6, the later K's top ends were an easy swap and will give you something no F2 owner has ever enjoyed, total peace of mind.

Have a look on EBay for a K4-K8 (actually, K7/K8 would be perfect) head and swap them over, and get yourself a mild cam that's gonna give you power where you need it, in the low to mid-range, not up there in the ionosphere where you'll seldom go. The F2 carbs (which are really good, by the way) will go back on using K7/K8 rubbers, and so will the F2 exhaust, and once you've painted everything black, no-one will ever know. Cheers, Terry.  

[B Raady]

Yeah, all of the above info is good mate, but don't panic, it aint the enf of the world. I've had all sorts of fun and games with my F2 resto and now I've settled on replacing the top end (cylinder block and head) from a K6, the later K's top ends were an easy swap and will give you something no F2 owner has ever enjoyed, total peace of mind.

Have a look on EBay for a K4-K8 (actually, K7/K8 would be perfect) head and swap them over, and get yourself a mild cam that's gonna give you power where you need it, in the low to mid-range, not up there in the ionosphere where you'll seldom go. The F2 carbs (which are really good, by the way) will go back on using K7/K8 rubbers, and so will the F2 exhaust, and once you've painted everything black, no-one will ever know. Cheers, Terry.  

Ha ha, Thanks Terry.  I'm not gonna lie, I haven't even ridden this thing around town yet...  I bought it over New Years and since it's so darn cold here I figured I'd update it a little.  I rode it before I bought it and it needs a tune-up pretty bad.  I'm just too anxious from not being able to ride.  Winter sucks...

You're right.....I need to settle down a little and have a cold beer.  Spring will come soon enough.  I'll stick to cosmetics for a while.

[Terry in Australia]

As long as you're not wearing cosmetics mate, no worries!

If it's running sh1t, give it a service (oil and filter change, air filter, points and plugs, adjust your valves and adjust your cam chain) and most importantly, clean your carbs. F2 carbs have push-in pilot jets and most blokes don't know that they can be pulled out and cleaned.

The pilot jets are tiny and you'll need a very fine wire (someone here said a fine guitar string works well) to clean them, and don't forget to strip the carbs and use plenty of carb cleaner and compressed air to clean out not just the jets, but the idle and choke circuits too. Do all of the above, and it should run very well. Cheers, Terry.

[B Raady]

As long as you're not wearing cosmetics mate, no worries!

If it's running sh1t, give it a service (oil and filter change, air filter, points and plugs, adjust your valves and adjust your cam chain) and most importantly, clean your carbs. F2 carbs have push-in pilot jets and most blokes don't know that they can be pulled out and cleaned.

The pilot jets are tiny and you'll need a very fine wire (someone here said a fine guitar string works well) to clean them, and don't forget to strip the carbs and use plenty of carb cleaner and compressed air to clean out not just the jets, but the idle and choke circuits too. Do all of the above, and it should run very well. Cheers, Terry.

Cosmetics only on Sundays and talking to you gearheads.

How else would the pilot jets be set in other carburetors?

[Terry in Australia]

How else would the pilot jets be set in other carburetors?

The K series pilot jets were screwed into their carbs, but (probably in an effort to stop people modifying them) Keihin "pressed" the F2 (and F3, K7 and K8) pilot jets in to the carb bodies, but you can carefully "twist and pull" them out with a pair of vice grips. Cheers, Terry.

[MCRider]

As long as you're not wearing cosmetics mate, no worries!

If it's running sh1t, give it a service (oil and filter change, air filter, points and plugs, adjust your valves and adjust your cam chain) and most importantly, clean your carbs. F2 carbs have push-in pilot jets and most blokes don't know that they can be pulled out and cleaned.

The pilot jets are tiny and you'll need a very fine wire (someone here said a fine guitar string works well) to clean them, and don't forget to strip the carbs and use plenty of carb cleaner and compressed air to clean out not just the jets, but the idle and choke circuits too. Do all of the above, and it should run very well. Cheers, Terry.

Cosmetics only on Sundays and talking to you gearheads.

How else would the pilot jets be set in other carburetors?

Its not the setting, they are what they are. But what Terry is saying, clean them.

[Yoshi823]

As long as you're not wearing cosmetics mate, no worries!

If it's running sh1t, give it a service (oil and filter change, air filter, points and plugs, adjust your valves and adjust your cam chain) and most importantly, clean your carbs. F2 carbs have push-in pilot jets and most blokes don't know that they can be pulled out and cleaned.

The pilot jets are tiny and you'll need a very fine wire (someone here said a fine guitar string works well) to clean them, and don't forget to strip the carbs and use plenty of carb cleaner and compressed air to clean out not just the jets, but the idle and choke circuits too. Do all of the above, and it should run very well. Cheers, Terry.

The question of the cam chainhas just reminded me of a situation a friend had with his 750K7. He pulled in to the pub car park and his engine was rattling really badly. I said that it sounded like the cam chain, and my friend replied that the bike shop had said the same thing, quoting him £500 for the job. I said that I would do it for the price of a pint of beer, so into the pub he went. By the time he came out the job was done and the engine was running, though one could hardly hear it. All that I had done was to do the correct procedure on adjusting the cam chain...which follows.
With the points cover off, align the 'T' marker. Remove the tappet covers on #1 cylinder. If the tappets are loose, go on to the next step. If the tappets arn't loose, rotate the crank 180 degrees and realign the 'T' marker. Replace the tappet covers. The next bit is more critical. Looking through the hole in the points back plate, rotate the crank very slowly until the trailing edge of the spring post for the advance/retard unit is adjacent to the static marker...this is about 15 degrees ATDC. Then loosen the nut on the cam chain tensioner lock bolt. Then back off the lock bolt. You may well hear the spring and the cam tensioner push bar as it applies. Lock the nut on the lock bolt. Job done.

If this dosn't cure the cam chain noises, then it's replacement time.

By the way, the procedure in the Honda Owners Manual is incorrect...it says in there to do the above procedure with the engine running, which has never worked as far as i'm concerned.

[Terry in Australia]

As long as you're not wearing cosmetics mate, no worries!

If it's running sh1t, give it a service (oil and filter change, air filter, points and plugs, adjust your valves and adjust your cam chain) and most importantly, clean your carbs. F2 carbs have push-in pilot jets and most blokes don't know that they can be pulled out and cleaned.

The pilot jets are tiny and you'll need a very fine wire (someone here said a fine guitar string works well) to clean them, and don't forget to strip the carbs and use plenty of carb cleaner and compressed air to clean out not just the jets, but the idle and choke circuits too. Do all of the above, and it should run very well. Cheers, Terry.

The question of the cam chainhas just reminded me of a situation a friend had with his 750K7. He pulled in to the pub car park and his engine was rattling really badly. I said that it sounded like the cam chain, and my friend replied that the bike shop had said the same thing, quoting him £500 for the job. I said that I would do it for the price of a pint of beer, so into the pub he went. By the time he came out the job was done and the engine was running, though one could hardly hear it. All that I had done was to do the correct procedure on adjusting the cam chain...which follows.
With the points cover off, align the 'T' marker. Remove the tappet covers on #1 cylinder. If the tappets are loose, go on to the next step. If the tappets arn't loose, rotate the crank 180 degrees and realign the 'T' marker. Replace the tappet covers. The next bit is more critical. Looking through the hole in the points back plate, rotate the crank very slowly until the trailing edge of the spring post for the advance/retard unit is adjacent to the static marker...this is about 15 degrees ATDC. Then loosen the nut on the cam chain tensioner lock bolt. Then back off the lock bolt. You may well hear the spring and the cam tensioner push bar as it applies. Lock the nut on the lock bolt. Job done.

If this dosn't cure the cam chain noises, then it's replacement time.

By the way, the procedure in the Honda Owners Manual is incorrect...it says in there to do the above procedure with the engine running, which has never worked as far as i'm concerned.

Yep, that's good info too mate, in fact, most times I've replaced a cam chain I haven't been able to find anything particularly wrong with the old one, but as the engine's already out, for the price of a new Tsubaki (26 bucks at Z1 last time I looked) it's cheap insurance.

Another "trick" is to pull the cam chain tensioner out and actually check it's operation, I've had several over the years that have been siezed, which only take a minute or two to fix, but I wouldn't put it past a dodgy bike shop to diagnose a new cam chain required, quoting a full "engine out" job, then just pull the tensioner out and give it a clean, and charge the unsuspecting customer hundreds of bucks for this 5 minute job.

It really is worth your while to be able to do a lot of this work yourself. Cheers, Terry.

[Whaleman]

http://forums.sohc4.net/index.php?topic=52277.0

I agree Terry. Dan