Topic: 1977 Honda 750 Supersport

[reliv77]

My newly acquired 1977 Honda 750  Supersport has some issues. The Bike will go into a High Idle at will and it has a slight Head Gasket Leak. I am in Cleveland Ohio. Looking to see if anyone knows a good mechanic in the Cleveland or surrounding area.

[flybox1]

you can fix the high idle issues yourself.
how bad is the gasket leak? 

[Old Scrambler]

Tell us a bit more..............how many miles............how long had it been parked before the recent startup..........completely original or.............

The high idle is likely one or more of the carb-slides hanging up.......may be from old fuel so its an easy fix with carbs still on the bike.

The leaky head gasket should be thoroughly investigated because few of the head gaskets actually leak..........its usually from dried-up internal seals below the cam tower........after you have cleaned the motor, observe where the oil is coming from and report back..........if it is the head gasket you may choose to live with it............if its a seal, it will only get worse.  Do some searching on this forum (google) about F2 and F3 top ends.....We are here to help.......

[reliv77]

The Odometer read about 4k but it is not the original Odometer. No idea how long the bike sat. When I drained the Tank the Fuel looked clean. I put in new fuel. As far as the Head Gasket, maybe I am referring to something different. I am talking about the top of the Engine that is held on by Philips Head Screws. There is just some minor leaking  of oil after I ride the Bike. The Bike is very Cleanand Stock looking, so I am guessing it has low miles on it.
Can you tell me how to investigate the carb-slides hanging up.

[TwoTired]

You can do valve cover gasket replacements with engine still in frame.  (But, you can't completely remove the valve cover without hacking on the frame or taking the engine out.)

High idle could be carbs needing vacuum sync.  Or there are intake/induction air leaks.  Or maybe it just needs a routine 3000 mile tune up.  I'd start with that.

[flybox1]

new set of allen bolts and a re torque might be all you need 

[reliv77]

I think I will try a new set of Allen bolts and a re torque and see if that works on the Oil Leak. Question, Would I need "Honda Allen Bolts" or could I find them at a Box Store or some other place.
If I go a step farther, and try and replace the Cylinder Head Cover Gasket, the Cylinder Head Cover Philips Head Screws are all I would have to remove to replace the Cylinder Head Cover Gasket? From the Post from TwoTired, it sounds more involved.
Still looking for some help on the carb-slides hanging up. If i could get some more details on that.

Thanks for the replies. Bear with me. I have never worked on a Motorcycle Engine before.
If it was a 1971 Ford Thunderbird, I could tell you where every bolt and nut are at.

[Old Scrambler]

Welcome......your a fast learner.......Yes, that is the valve cover and it appears you already have allen-head screws.....If they are stainless steel, they are prone to losen so re-install with some blue locktite......be sure to check them all.

The easiest way to begin to cure the hanging-carb issue is to put some Sea Foam or a few ounces of fuel-injector cleaner in your tank.......and then go for a 50 mile or longer ride.  If that does not cure the idle problem, get the bike running and hold at a constant rpm at or just above idle....spray the manifold rubbers with WD-40 and look for immediate dry spots as well as an increase in the idle speed.......if found either tighten the clamps or replace if cracked.  BTW....are you sure you have the choke completely OFF?

[TwoTired]

Allen bolts are far easier to over torque than cross head screws.  And aluminum is softer than steel.  Don't over torque in hopes of  extending hardened rubber service life at the risk of helicoling stripped threads.


For the random high idle, begin with a 3k Tune up, and vacuum sync.
Then look for intake vacuum leaks.

What do you base the "carb-slides hanging up" diagnosis upon?   You know, you can pop off the top of each carb and squirt penetrating oil on the slide bores.  This will dilute gummed carb slides, if that is the real problem other than out of tune/out of sync, or intake leaks.

Cheers,

[piute]

   I myself had a high idle (F2)
 All my boots were hard boiled them in some green(works wonders) I cleaned the carbs 3 different times ,slides and all jets  all stayed stk. no changes,But new diapham kit instal;ed, Set sliders to 1/8" using an 1/8 inch drill bit(have sync tool yet to use) Hey why mess with a great thing there doing fine cam chain bit noisy though.Everything seems fine still,"O" all new cables removed throttle return cable (not advised if not ridden lots of miles and know when to use kill switch.

[reliv77]

From the suggestions on this Post I think I will try the minimum:
1) Try a new set of Allen bolts and a re torque the Cylinder Head Cover. Again, are these Bolts available through Honda in Allen?  Maybe find them elsewhere? Is there a Tork Spec for these Bolts?
2) Try some fuel-injector cleaner in the tank.
3)Pop off the top of each carb and squirt penetrating oil on the slide bores.
Good for Starts?

[Stev-o]

The socket head screws are not stock and can be purchased at a local specialty bolt company. I believe they are 6mm and various lengths. 

Try Hexagon...

http://www.hexagonindustries.com/

[reliv77]

Thanks for the replies. Bear with me. I have never worked on a Motorcycle Engine before.

Still debating on replacing the Cross Head Screws with Allen Bolts and a re torque the Cylinder Head Cover for the slight Oil Leak. Would I likely Strip the Threads in doing so?
Also now seeing another slight oil leak from one of the eight large silver "Cap Bolts" on the Cylinder Head Cover. I do see O rings on these. Assuming they are replaceable O Rings?
I am also assuming that I can not take off the Cylinder Head Cover without first removing the Engine from the Frame???

[Don R]

If you try to tighten the cross point screws be sure to find the proper screwdriver bit. Most of the problem people have is use of the wrong bit. They are not auctually phillips heads they are a Japanese equivalent. JIS. I usually tell people to find the screwdriver that looks perfect and then use the next larger one. You can try to tighten, usually doesn't work. Use the google search function here. Almost everything has been gone over multiple times. The FAQ, and tips and tricks section is great.

[bollingball]

If you try to tighten the cross point screws be sure to find the proper screwdriver bit. Most of the problem people have is use of the wrong bit. They are not auctually phillips heads they are a Japanese equivalent. JIS. I usually tell people to find the screwdriver that looks perfect and then use the next larger one. You can try to tighten, usually doesn't work. Use the google search function here. Almost everything has been gone over multiple times. The FAQ, and tips and tricks section is great.

http://www.instructables.com/id/When-a-Phillips-is-not-a-Phillips/?ALLSTEPS

[reliv77]

What would be the Tork Spec in pounds for the Allen Bolts to re torque the Cylinder Head Cover?

[reliv77]

TwoTired stated that I could:
 "You can do valve cover gasket replacements with engine still in frame." Do I Loosen all the Bolts and "Fudge" the new Gasket in? Cut the Gasket? Use any type of Gasket Seal?

Also:
"Or maybe it just needs a routine 3000 mile tune up.  I'd start with that."
What is all involved in a 3000 mile Tune Up? Points, Plugs, etc?

[Jiminy Indy]

You can remove all the bolts holding the valve cover on and there is just enough room to lift it up to replace the gasket. But it's a tight fit and you cannot remove the vlave cover completely without removing the engine completely from the frame which is a real PIA.

You shouldn't need any gasket seal. There are a couple guide posts that the gasket fits over so it will fit correctly. Make sure you hit these posts or it will surely leak. And use an anti-seize on the bolts holding on the cover.

[Jiminy Indy]

And there's lots of S/S allen head bolt kits on e-bay for about $30 or so that replace all the engine bolts. I personally replace all the standard bolts with allen heads. Not as much chance to riun the heads - and besides I like the looks of the shiny allens against the black engine - but that's just personal preference.

[reliv77]

Would the Gasket be available at a Honda Dealership or would I have to hunt for one being the age of the Bike.

[Jiminy Indy]

Lots of SOHC websites around but try this guy. Cost is $6.95 plus the trip.

http://newmotorcycleparts.com/gaskets/valve_cover_gaskets.html

[reliv77]

Jimmy Indy, Thanks for the Link to (http://newmotorcycleparts.com/gaskets/valve_cover_gaskets.html)
Saved a Ton of Money compared to a local Honda Dealer.

[reliv77]

If i take the advise of checking the carb-slides hanging up issue. Would I need a new gasket once I open the Top of the Carbs?

[TwoTired]

If i take the advise of checking the carb-slides hanging up issue. Would I need a new gasket once I open the Top of the Carbs?

Normally, no.

[reliv77]

OK. Put some Sea Foam in the Fuel Tank today. About three ounces in a Half Full Tank. Went for a 5 mile ride. Had to limp back home to the house on the last 1/2 mile. The bike would barley run. It was running a whole lot better before the Sea Foam. Any Ideas why?

[bjbuchanan]

The seafoam loosened up all the crud

[Don R]

You don't cut the gasket, you put one end over the rocker/cam  cover and slip it under the cover then do the other end. Then carefully align it with the shape of the cover and slip it over the dowel posts. The hard part might be cleaning off the old one.
 The seafoam might have loosened goo and/or rust in the tank. There was originally a screen inside the tank over the fuel petcock. It may or may not still be in there, if it is it might be covered with gunk of it it's gone the gunk may have made it into your carbs. It was inevitable if it is that problem.
The seafoam might have hurried the process.

[Jiminy Indy]

Prolly a good idea to take off your petcock and clean it out anyway. Plus fuel line filters are a cheap and easy way from any gunk getting to your carbs. I like the cleat glass ones at JP Cycles since you can see when they start to gunk up and the filters are replaceable.

[reliv77]

I took the Fuel Tank off and the Petcock. Drained all the Fuel into a Glass Jar. The Fuel looks Super Clean. Wondering if I should still add the Seafoam to a new tank of Fuel???

[TwoTired]

I've tried seafoam several times and have seen no measurable effect other than the engine being down on power due to reduction in energy content of the diluted fuel.
If it's clean, seafoam won't make it any cleaner, anyway.

I know many people swear by seafoam.  It's never done anything for me or my bikes except make my wallet thinner.  A miracle potion it is not, imo.

If you still have the in tank fuel filter in good shape, that's all you need.  Filtering it twice or 3-10 times won't make the fuel any cleaner.  Further, inline filters can get restrictive as they accumulate particles leading to another set of issues.   And, if you don't route the lines correctly, the gravity feed fuel system can't work correctly.
In line fuel filters are cheap for a reason.  They cost even less to make than to buy.

Have you yet completed the 3K tune up schedule and vacuum balanced the carbs?

If you had a problem mid-ride, then take a look at the spark plug tips and check the exhaust head pipes for even heat.

Improper adjustment of points can certainly make the bike "limp".

[reliv77]

That is what the Bike seemed to do with the Seafoam, loss of power. When I pulled the Petcock out of the Fuel Tank, the only thing I saw was a short Plastic Pipe connected to the Petcock. Would the Original Fuel Filter be there? I do have an external Fuel Filter (clear plastic) and it looks really clean.
Still have not done a 3K tune up or Vacuum Balance.
What is all involved in a 3K Tune Up?
No idea how to do a Vacuum Balance.

[TwoTired]

That is what the Bike seemed to do with the Seafoam, loss of power. When I pulled the Petcock out of the Fuel Tank, the only thing I saw was a short Plastic Pipe connected to the Petcock. Would the Original Fuel Filter be there?

Should be. Could be.  It also could have been destroyed by Mr. ham hands during it's life when trying to remove it, and a cheap filter then put in to recover from their flub.  The original filter fits pretty tightly in the tank bung (look very closely, shine a light in the hole) and doesn't usually come out with the fuel valve on your model bike.

Still have not done a 3K tune up or Vacuum Balance.
What is all involved in a 3K Tune Up?
No idea how to do a Vacuum Balance.

Well then, stop complaining about poor performance or run issues until you do the basic maintenance. 
 You got some learning to do and shop manuals to read!! 

Cheers,

[736cc]

That is what the Bike seemed to do with the Seafoam, loss of power. When I pulled the Petcock out of the Fuel Tank, the only thing I saw was a short Plastic Pipe connected to the Petcock. Would the Original Fuel Filter be there? I do have an external Fuel Filter (clear plastic) and it looks really clean.

The Supersport fuel strainer/filter is inside the tank; its in the threaded petcock mount and difficult to remove without mangling it. New from Honda it comes w/ a new o-ring.

[reliv77]

I am not complaining about poor performance. I am here posting to learn from you guys ( the best source I have come across). I tried to download the PDF Shop Manual from this sight, but it will not download for me.  Where can I find a Shop Manual for a 1977 Honda 750F Supersport? Are the Tune Up Parts available through Honda Dealers or are there better sources?
 Thanks for all the help so far.

[TwoTired]

I am not complaining about poor performance. I am here posting to learn from you guys ( the best source I have come across). I tried to download the PDF Shop Manual from this sight, but it will not download for me.  Where can I find a Shop Manual for a 1977 Honda 750F Supersport? Are the Tune Up Parts available through Honda Dealers or are there better sources?
 Thanks for all the help so far.

You can buy a paper copy of the CB750 Shop manual from helminc.com
I don't think there is a "better" source for Honda components than from Honda... that is, when they still have the item in stock.  Some of the parts on 30-40 year old models are discontinued.  It doesn't hurt to ask them.
However, if there is enough demand, they will make more parts.  They are businessmen.
Lots of parts are only profitable to make when there are high quantities.  If it costs $5000 to set up a production run of parts, they aren't going to set up to make 10 parts @ $50 each.  There are also costs for storing unsold parts, which eat into the profit line.  So, making a bunch just to sit in warehouses doesn't make sense, either.  However, if there are 100,000 requests for a certain part.  They will make more parts.

So, you cheap bastards (you know who you are) that are trying to save a buck on substandard aftermarket parts are contributing to the number of "discontinued" items from Honda!   

Cheers,

[reliv77]

On ebay there is a:
"Clymer Honda In-Line Fours CB750 SOHC Manual M341 Honda CB750F Super Sport 75-78 Service / Repair Manual" for sale. Seems to be more related to the Honda 750's for $33.26. Looks what I need?

[Jiminy Indy]

The Clymer & Haynes versions are both good. I have both plus the Honda Shop Manual & the HondaMan book. In my opinion the Clymer & Haynes are more directed toward us rookie-tpes and the Shop Manual toward the Honda mechanic. Just a little different perspective is all. They are all good and all have the right information. Just my 2-cents worth.

[TwoTired]

On ebay there is a:
"Clymer Honda In-Line Fours CB750 SOHC Manual M341 Honda CB750F Super Sport 75-78 Service / Repair Manual" for sale. Seems to be more related to the Honda 750's for $33.26. Looks what I need?

It's better than nothing, but not nearly as good or as accurate as the Honda shop manual.  I have both the Honda and Clymer manuals and I seldom use the Clymer, it has mislead me far too often to trust.

I would agree that the Clymer is more directed at the newbie.  But, there is just plain wrong stuff in there which, imo, is hardly beneficial to the newbie.

Cheers,

[CafeDawg]

reliv77  I would try to download again if not here then their are other sites with them as well, for free.  Remember Google is your friend.  This site has a lot of info and can be overwhelming, I know it's taken me three years just to start understanding terminology and some of the specific design of these bikes.  You need to do a lot of reading and searching if you are going to get involved in fixing your own bike.  That being said the info and help is here but you need to look at FAQ area and the sellers area to start getting an idea of what can be done and where parts can be sourced from;  ebay is one option, dealership is another, Partsnmore, bilebandit, oldbikebarn, 750supply, CSML, are others.

A couple answers to your question....The cap that is leaking is the Tappet cover I think and new gaskets are available at a number of places.  To Vacuum Synch your carbs you need a specific tool with four gauges, one for each carb, about a $70 piece and their are links here and Youtube showing how to use it.  Their is a member here who puts together allen kits specific for their model.   The manual has torque specs for almost all the nuts and bolts on the bike so you won't over tighten anything.

To get it running right is a process, just like the Tbird...oil,fuel, plugs. airfilter good places to start.  I'm sure Cleveland has someone who can synch the carbs for ya.  Also the is a mix screw with a knurled end up by the carbs which might be misajusted which can affect idle. 

Just take your time and try and sift through all the info here and the suggestions people throw at you.  In the end I find it's worth all the effort!

Respect
CD