Topic: '77 750F. off the back burner, on to the front.

[BCBarker]

So the beer runner is finished short of a wooden crate to hold the beer...

Looking ahead to the next build, I recently picked up a 77 750 for a great price. I know the "black motor" is the bastard child of these bike and known for throwing valve keepers and trashing the head. My question: is it worth tearing into the motor and fixing this on a low mileage (13k) bike? Or would I be ok fixing all but the frame And motor, then tackling those in a coming winter... When there is say 20k on the clock... Opinions?

[Stev-o]

I would do a start up first to see what you have. 13K miles is low, and unless abused, you may be good.
That bike looks pretty good and complete, a good seat would go a long way.

[rickmoore24]

I agree, check the compression and if it's good do a tune up and oil change then go clock those 7K miles if the rest of the bike is roadworthy. 

[BCBarker]

That's what I was thinking. Just wanted to throw it out there for opinion sake. Didn't know if there was a "don't trust the grenade motor" feeling or not. From what I've read here and DoTheTon it usually fails around 30k so I figure I have time.... Knock on wood... For now I'm starting with compression test, carb tune up, front end rebuild,brakes, tires, and a Corbin Gunfighter.

Any idea if this stock exhaust is worth anything? The muffler is ridiculous in size!

[MCRider]

That's what I was thinking. Just wanted to throw it out there for opinion sake. Didn't know if there was a "don't trust the grenade motor" feeling or not. From what I've read here and DoTheTon it usually fails around 30k so I figure I have time.... Knock on wood... For now I'm starting with compression test, carb tune up, front end rebuild,brakes, tires, and a Corbin Gunfighter.

Any idea if this stock exhaust is worth anything? The muffler is ridiculous in size!

You could probably buy a ebay head, have it refurbed and swap it out come winter. Unless you're looking at more work.  From what MRieck (head guru) and others say here, the newer parts last longer. Probably longer than you will with this bike.

Have Fun.

[BCBarker]

So I've finally taken this off the back burner and started to see what lies under the dust and rust. It will be a slow build, but hopefully steady. I've been gathering parts for a few months now so I just need time now.

Started to dive into a spare set of carb thinking I'd rebuild those and just swap them with the ones that came on the bike.

All went well with the cleaning and disassemble except two of the cross over vent hoses tore when I was removing them (#7 in the part fishe).



Can I replace with standard 1/8" fuel line? It seems that these have a brass tube inside. Do I need to use that on new fuel line?

[MCRider]

re: fuel line. Honda fuel line is 5.5mm which has no common inch counterpart. 1/8 too small; 1/4 too large. MANY people cram the 1/8 on or ziptie the 1/4 on. I have 5.5mm i bot to sell to the forum. Its clear and my cost is $2.5 ft. Too pricey for some, but if you want the correct stuff this is it.  I bot a big roll from a snowmachine shop online.  Some people will buy it in a heartbeat, others will say you'll never catch me spending that much...

Your call.

OEM fuel line in black is still available from Honda.

The copper pipe is a mystery. Unless it's a nipple that pulled out of the piece it should be in, stuck in the fuelline, like a petcock or float bowl. Often happens esp when the 1/8 line is used.

[SOHC4 Cafe Racer Fan]

MC,

How many feet do you need to comfortably fit?

[BCBarker]

MC, pm sent for the fuel line. Thanks!

[MCRider]

MC,

How many feet do you need to comfortably fit?

Come again? 

[MCRider]

MC, pm sent for the fuel line. Thanks!

OK, I'll take a look.

[madmtnmotors]

So I've finally taken this off the back burner and started to see what lies under the dust and rust. It will be a slow build, but hopefully steady. I've been gathering parts for a few months now so I just need time now.

Started to dive into a spare set of carb thinking I'd rebuild those and just swap them with the ones that came on the bike.

All went well with the cleaning and disassemble except two of the cross over vent hoses tore when I was removing them (#7 in the part fishe).



Can I replace with standard 1/8" fuel line? It seems that these have a brass tube inside. Do I need to use that on new fuel line?

Check the ones you tore, I believe these are the accelerator pump crossovers. If so, these have unobtanium brass restrictors inside the tubes to provide for proper operation of the accelerator pump circuit. Check the damaged tubes carefully.

[BCBarker]

[/quote]

Check the ones you tore, I believe these are the accelerator pump crossovers. If so, these have unobtanium brass restrictors inside the tubes to provide for proper operation of the accelerator pump circuit. Check the damaged tubes carefully.
[/quote]

Yeah. I think you are right. I can cut out the brass. You think I can slip it into a new fuel line and be ok?

[brandEn]

That looks like a good bike for sure. The 77-78 F's are known for valve guide wear. So if anything your engine will burn a little oil and smoke on cold start so I wouldn't sweat a complete rebuild at only 13K. I think the guides typically didn't become a problem until around 30k so get her going and put a some miles on her and then see where your at. I am betting once you get some routine maintenance items taken care of and some cleaning it will run great. No worries about it grenading or anything like that.

[BCBarker]

That looks like a good bike for sure. The 77-78 F's are known for valve guide wear. So if anything your engine will burn a little oil and smoke on cold start so I wouldn't sweat a complete rebuild at only 13K. I think the guides typically didn't become a problem until around 30k so get her going and put a some miles on her and then see where your at. I am betting once you get some routine maintenance items taken care of and some cleaning it will run great. No worries about it grenading or anything like that.

Thanks BrandEn. That was my thought too. Glad to hear that is the general consensus too.

If all goes well and I can get in wrench time, I'm hoping for a spring/early summer completion. Aside from tires, I have gathered all wear items from brakes to grips. So it just a matter of time, which is sometimes scarce.

As for the carb vacuum pump circuit, when I cut open the broken tubes there are small 5/16" long brass tubes inside. I'm guessing its to keep the rubber hoses from collapsing under vacuum. Any reason I shouldn't just push them into new rubber lines? Not looking to spend $70 on OEM rubber lines!

[madmtnmotors]

Any reason I shouldn't just push them into new rubber lines?

As long as the replacement rubber lines are sized for a snug fit I don't see why not.

[BCBarker]

Awesome. Thanks!

[Free Booter]

cool idea actually.

[SOHC4 Cafe Racer Fan]

MC,

How many feet do you need to comfortably fit?

Come again? 

How much length of line is required?

[MCRider]

MC,

How many feet do you need to comfortably fit?

Come again? 

How much length of line is required?

Depends on the app. and how accurate are your cuts.

Rt side/Lft side petcock; 1 hose / 2 hose and misc hoses.

2-3 ft?

[BCBarker]

Put a little time into the bike today. Got it to run and idle. With the choke on it seems to have oil coming out of the exhaust. Not sure if this was from the PO putting some oil in the cylinders or if I have bigger problems. Do these suffer from valve seal failure at low mileage? ill post some pics tomorrow.

[madmtnmotors]

I think the valve seals could be suspect, but more due to their age than the mileage. The rubber gets brittle and cracks with age. I've got a 78' 750F with over 40,000 miles and all I've done is replace the valve seals when it started smoking on startup. No problems since. Replaced the rubber "coins" under the cam towers while I was at it since the motor was out anyway. When I replaced the valve seals they were so brittle that they actually shattered as I removed them.

[BCBarker]

I'm guessing you have to pull the motor/head to fix the valve seals?

[madmtnmotors]

Yes, the valve cover will not clear the frame tubes. The use of a hook with an engine hoist can help. I can start with a fully assembled/running bike and have the engine on a stand in an hour and a half with the use of a lifting hook. Made mine from scrap tubing laying around the shop one afternoon...


http://forums.sohc4.net/index.php?topic=115643.msg1303546#msg1303546

[BCBarker]

Finally got some time to do a little. Started to tear down the front end. Forks were worse than I thought. Some light pitting. Thoughts on replacing these?

EDIT: after a little steel wool, the "rust" was really just from the tripple. Only light pitting above the main sweep area of the seals. I'm running with these for now.



I've recently gotten a powder coating connection so lots of fresh powder to come! Might do a little mock up at work to think through some ideas... Stay tuned!