Topic: Terry's Effing F2, return of the prodigal SOHC4?

[grcamna2]

Terry,
How does your F2 compare with your K0 in power ?

[Terry in Australia]

Thanks Bill, I haven't ridden them back to back so it's hard to say. The F2 is very linear in acceleration, especially with the pumper carbs, but the K0 feels more "Raw", and even though they're both running Delkevic pipes, the K0 has a much harsher note, which of course could just be that there's less baffle material in the muffler, but if I had to sum them up I'd describe the K0 as "Raw" and the F2 as "refined". That's not really too surprising considering that the F2 was the final development of the CB750. 

I like them both, the F2 has much better brakes and probably handles a little better, but the K0 is more fun to ride, I think?

[Don R]

 
My F1 seemed like a bigger bike than the K0, but the K0 seemed more nimble. Probably something to do with fork offset.  It also had a lot more braking power but I did double fronts on it.  I theoretically traded work on a gl for another F1 with a 900 kit. Getting it out of my brothers garage is an altogether different problem. 

[Terry in Australia]

I think you're right Don, working on my F2 today, it feels like a much more modern bike, and physically bigger bike than the K0. As opposed to the K0, on the F2 I feel like I'm sitting "on" it, not "in" it.

[Terry in Australia]

Well I've sold a few things lately, my leftover K0 parts, and a big old collectable chainsaw, and between them I've become $3300 (AUD, about $2400 USD) richer. Anyhoo, I saw a post on the Aussie CB750 FB site where a guy here bought an F2 with an engine in pieces, sh1t seat, no exhaust, crappy paint etc, for $3500. I replied that I have an F2 that has lots of "patina" but good running engine, new tyres, Delkevic pipe, etc that I'd previously have sold for $3500 but after seeing what you get for $3500 now I'd have to put the price up.

Within hours I had 3 guys contact me wanting to buy mine. The first guy agreed that $4500 was a fair price, so I've told the other two that I might be able to put something together for them too. They're all Cafe Racer fans, so I doubt that the F2 will get restored, but no biggie, it's an F2 not a K0, so I can live with that. The only problem is the buyer wants to ride it home, so I've been farting around with the carbs trying to stop some leaks. I've had 2 sets of carbs on this bike and they've both leaked and driven me nuts, I personally believe that the non-removable float valve seats are damaged in a couple of them, but I decided to pull them apart and check the float levels again to see if it was something simple.

I pulled the carbs off and the first thing I noticed warmed my heart, could the fuel leaks be as simple as this?

F2 Carbs 14 Nov 2021 by Terry Prendergast, on Flickr

It may have been a contributor but it wasn't the only problem. I dropped all the floatbowls and the carbs internals were as clean as a whistle, so I just adjusted the floats, which were maybe .5 - 1mm out. I sat them upright in my vice with a remote tank that I filled with fuel, and gas pissed out of carbs 3 and 4.

F2 Carbs 14 Nov 2021 2 by Terry Prendergast, on Flickr

I pulled the float bowls of #3 and #4 and replaced the float valves, and tried them again, and this time only #3 leaked. Yay! I pulled #3 again and changed out the float valve again, but no dice, still leaks. Fcuk. Ok, the other carbs (this bike's original carbs) that I'd rebuilt with new kits last year were calling me, so I set them up on my vice, hooked up the fuel line, and they leaked from #3 as well. I pulled #3's bowl, changed the float and the valve out, reassembled the bowl, set it on my vice again, hooked up the fuel line, and #3 pissed out fuel again. Fcuk.....

Back to the carb pile. I've got another complete set of F2 carbs that I marked, "Cliff's carbs, 115 mains". "Cliff" is a member here, and many years ago I did a bit of work on his F2 Cafe Racer for him, but can't remember why I have his carbs? Did I swap them out for some reason? Did I put new CR's on his bike? I can't remember. Anyway, I set them up on the vice, hooked up the fuel line, and it only had an intermittent leak from #1 carb, which stopped when I tapped the bowl. I decided to replace that float valve anyway, and while I was at it I popped off #3 bowl just to make sure fuel was actually getting in, and was happy to see that it had fuel in it, and so I took it back to the garage, set it up on the vice again, refilled the remote tank, and this time, no leaks. Sweet..........

By this stage I'd been fcuking around for almost 4 hours, my back was killing me, and I needed a drink, so I packed up and came inside. I'll check them again tomorrow, if the fuel level in the line hasn't dropped, I'll call them good, check the air screws and adjust as necessary, and give them a spray of WD40 and install them, fire the bike up and see if it's going OK. If it is, I'll call it good and tell the new owner to come pick it up, or that I can't figure it out and to forget about it, unless he wants to trailer it home. If it does run well, I'll be taking it for a ride to shake out any other issues before I hand the keys over to him, and bank some more bucks.

I'm happy to say that I'm using only the best quality products, just take a look at my new fuel line

F2 Carbs 14 Nov 2021 1 by Terry Prendergast, on Flickr
 

[RAFster122s]

Very good fuel line, claims so itself…so you are right as rain…

[Alan F.]

I spotted this over on vintagehondatwins.com, maybe you can save some work on some of those leaking carbies?

[jgger]

Very interesting! Thanks for posting, I will have to remember this one.

[Hoosier Honda]

I spotted this over on vintagehondatwins.com, maybe you can save some work on some of those leaking carbies?

Pretty cool tip there, I'm surprised it works that well.

[krusty]

That's an old trick known among old hands and related to me many years ago. I've never needed to try it but I did hunt around for a ball small enough to try it but didn't have one.

[Terry in Australia]

Thanks Alan, I might give it a try if I ever use those other carbs again. (I’ve decided that I hate PD carbs now, which is a shame, as I quite liked them before yesterday)

[Don R]

 I was sorting a box of junk and thought I saw a tiny bearing ball. I thought of this, reached to grab it and it got away. Or it was an illusion.

[grcamna2]

I was sorting a box of junk and thought I saw a tiny bearing ball. I thought of this, reached to grab it and it got away. Or it was an illusion.

A single ball bearing can have quite an extended path of travel once it falls out of your grasp Don 

[Terry in Australia]

Well just a warning to everyone regarding the "Ball bearing trick", on PD carbs, don't fcuking do it! I drove over to my local bearing supply shop and bought a few 4mm ball bearings, I felt too embarrassed to just buy one, but interestingly, the guy behind the counter had heard of "the ball bearing trick" for motorcycle carbs and sold a few for that purpose.

Anyhoo, I took my 2 dollar purchase home and pulled out the carbs that were leaking the most, popped off the float bowl and removed the float pin, float and float valve. The 4mm ball was the perfect size as it sat on top of the hole for the tip of the float valve, so using a brass drift and a small hammer, I gave it a little tap, and it felt like I'd pushed the ball down into the hole? WTF? I removed the drift and checked the ball, but no, it wasn't stuck in the float valve's hole? Ok, well looking at the hole, it didn't look any different than before, so I gave it a couple more taps, and once again, it felt like something was moving? I checked again, the ball was loose on top of the hole in the float valve's seat, so no problems, so I did a little more tapping, and while it didn't look like I'd made any difference, I reassembled everything, but noticed that the float was now drooping down well below the standard 14.5mm float height, and I had to "adjust" the float height by bending the tab on the float at maybe a 45 degree angle?

Then it dawned on me. The PD carb's float valve seat is pressed into the body of the carb, and what I was doing as I was tapping away was pushing the seat further down into the casting! Fcuk! Oh well, I screwed the float bowl back on and tipped the carbs upright, hooked up the fuel line again, and...... it still leaked, like a seive.

So the bottom line is, NEVER do the ball bearing trick on PD carbs, unless you want to ruin your carbs. The "Trick" probably works well with screw in seats (like the ones in the video) but is not only useless on PD carbs with pressed in float valve seats, it will ruin them. Luckily for me I have several sets of carbs so I just grabbed another set to put back on the F2, but if I only had one set, I would have been extremely pissed off. I'm wondering if the pressed in seats are available, and if so, if I can remove the old pressed in seat with a sheet metal screw? Obviously that will ruin the seat, but if you can find a new one to fit, it should fix the leak. Either way, NEVER, EVER, use the above method on PD carbs, or you'll be heading straight to the Pissed Off thread.      

[RAFster122s]

If the seats are pressed in can you pull one that’s toast and then make a new one on the lathe???

[Terry in Australia]

If the seats are pressed in can you pull one that’s toast and then make a new one on the lathe???

Yep I had the same thought David, I might do that if I have to, but I'll check my parts manual and see if there's one I can buy, the hardest part will be removing the old one.  

[Alan F.]

I've wondered why not epoxy the 4mm bearing to a narrow tube and rub the valve seat with lapping compound?

Sorry to hear your bad experience Terry, maybe I should've kept that one to myself?

If you make one seat and it works, I guess there's another part to add to your catalogue.

[Don R]

 I've seen charlie the guy that assembled my sandcast walking around the shop hand lapping a needle into it's seat.

[Terry in Australia]

Well the buyer is coming over on Sunday to pay for the effing F2, so I thought I better go check to see if it’ll start, and was happy that 1. Cliff’s carbs weren’t dripping fuel all over the garage floor, and 2. It started right up.

I had thoughts of working feverishly today and tomorrow to get it running properly, but it’s going ok with the new dyna ignition and battery I installed this week, so instead I’ll leave it alone. Tomorrow I’m going for a ride with Spotty on my two Triumph Rocket III’s, and Sunday I’m selling the F2, for just about what it costs me. Can’t really complain about that!

[Terry in Australia]

Regarding dribbling PD carbs, all the ball bearing tapping is doing is reshaping the seat, and as tapping a ball bearing into a “floating” seat isn’t practical, if I ever need to do another set, I’ll lightly clean up the seat with a drill. Just a light touch to clean up the seat should do the job.

[grcamna2]

Selling that F2 Terry? You won't miss it ?

Have you ever used a cotton swab with a tiny bit of very fine lapping compound(or toothpaste?)to touch-up a float valve seat?

[Terry in Australia]

G'Day Bill, nope I don't think I'll miss it, it's not my old F2 like I thought it was when I first bought it, and I need to raise a lot of dough to pay for Davey's Harley, which means a lot more to me. I've never cleaned up a float valve seat that I can remember, I've replaced a few in K0-K6 CB750 carbs (they used to come in quality rebuild kits) but really it's only been PD carbs that have been a problem in that regard for me?