Topic: A few more newbie questions

[ilovemy78]

Checked several of the faqs first   I am truly a newbie so please be gentle.

So I have this awesome '78 Cb750 with 9100 miles...I love it...absolutely love it.  A few things I'm wondering about to love it more:

1. Can I take the stock bars and drop them?  I did this with an '80 yamaha sr500 and although it looked cool and helped me be more aerodynamic the bars would hit the tank if i turned too sharp  

2. I have not ridden a motorcycle since this '78 in many years and I feel that it is a bit sluggish.  I'd like to do a few things to speed it up some.  Right now it is 100% stock AFAIK.

3. Any concerns removing the crash bars? (other than the obvious)  The bars on my bike are rusty and ugly and I'm not one to drop the bike (unless someone decides to hit me).   I'd also imagine it would help out an itty bit on power removing that extra weight.

4. The choke/idle is iffy.  Bike takes too long to warm up- maybe 10-15 minutes before idle goes to normal (80-90 degree days).  Not sure if this is an easy diagnosis or not.  The bike is almost sketchy to drive if i'm riding from a cold start (lurching forward, etc).  Maybe this is just the way it is but thats what I want to know

5. I am using 94 octane in the tank.  The dealer told me to put in some sort of additive.  Is this necessary or will it help, or...

6. The motorcycle dealer I got the bike from told me a few things I just want to make sure of as I'm an itty bit suspicious.  He told me I had to start the bike every single day no matter what and run it or else "it may not start again".  he said this will also happen if I don't turn off the fuel after every ride.  he said I'd probably have to bleed the carbs if I don't turn the fuel off after every ride.  He was extremely insistent that the bike wasn't going to run right otherwise.  He countered everything I said with "dude, its 30 years old, what do you expect?".   I'd prefer to fix these things if possible ...its no sweat turning off the fuel line but...I'd rather not if I can address the problem.  I also don't want to bleed the carbs everytime I forget.

Thats good enough for now.

Thanks much!

[gold72]

Drop those bars, just watch the clearance on your tank

I would stay away from fuel additives (except for seafoam) you dont need to run 94 octane

I always shut my fuel off when I turn my bike off, just get in the habit of doing it and it will be second nature

don't know why you would have to start your bike every day?

good luck and post some pictures (and get rid of those ugly crash bars  )

[ieism]

If the bike hasn't been run in a while, and it's just been standing at the dealer for a long time it will probably not run as good as it should for various reasons. A 750 in good tune should pull strong troughout the revrange, and not feel sluggish anywhere.

The good news is, it runs already. The poor idling can have many reasons. I would ride it a lot for a few weeks, get the cobwebs out, and see if it improves. It may just be dirty carbs or a weak battery. My bike sucked the first few weeks, until I took it on a couple of long trips, and it started running a lot better.

You don't need to start it every day normally. If you do, there's something wrong (battery?).

[medic09]

Welcome!  Sounds like you got a great bike.  The K8 is the top of the SOHC evolutionary ladder (right Eldar?).  

1.  You can put lower bars on; you can put higher bars on.  There's a limit, but you'll find it.  The tank is obviously much wider than your SR500.  (I had one of those; GREAT little bike.)  If you look at the cafe bike threads on here, you'll see all sorts of possibilities.  I'm a sit up and beg rider, myself.
2.  Sluggish?  Well, it is a bit heavier than the SR500.  Having said that, a proper once over is in order before any judgements.  Change the oil, check the tire pressures, clean the carbs, tune it up (valve clearances, timing chain, points, etc).  All that will really just take an afternoon, but then you can have a better idea of how you're running.  Is gas flowing okay from tank to carbs?
3.   Crash bars (if you mean engine guards) are not an integral part of the bike.  If you don't like 'em, get rid of 'em.
4.  These are very cold blooded bikes.  My particular bike takes 10 minutes or more to warm up; 5-10 on really hot days.  Even after you clean and tune it up (do that first!), you may find it to be quite cold blooded compared to other bikes.  Nature of the beast, but not a problem except for warm-up.
5.  Personally, I use low or medium octane.  I run SeaFoam through a few times a years.  High octane may be too high for your stock motor.
6.  Your dealer is an idiot.  Sorry, I shouldn't say that.  If you have a fresh battery and the charging system is working, you do not need to start it every day.  In fact, since it only charges at riding rpms, not idle, just starting it will run the battery down.  But you should ride it every day, well, just because a great bike should be ridden.    Seriously, mine often sits a week or two while I ride my 'daily' bike, and it is fine.  Just put it on a battery tender once a month.
     If the carbs and petcock on the tank are working properly , you do not need to close the fuel tap every time.  I don't, and have never had a problem for the roughly 20,000 miles I've put on my bike so far in the last two years.  I don't bleed my carbs, though I probably should before the 3 months or so that I don't ride in the winter.  The '30 years old' comment is a stupid cover for 'I don't know if it has been properly maintained.'

Have some fun.  Take a day to do complete front to back maintenance.  Get to know your bike.  Come back with questions and stuff to share.  This is a great forum.

Folks who know more than me will be by shortly with better advice.  My advice is worth exactly what you paid for it.  

[MacM2010]

I'll take the crash bars, don't care what they look like.

[TwoTired]

1. Can I take the stock bars and drop them?  I did this with an '80 yamaha sr500 and although it looked cool and helped me be more aerodynamic the bars would hit the tank if i turned too sharp  

You mean replace the Bars?  yes  But, it seems silly to allow the bars to contact the tank.  If the bike falls over, even on soft ground, you now have a dented tank!  Also, consider that the cables and hoses are the correct length now.  Where will the extra length go? Bunching up cables usually makes the cables harder to operate.  Who needs a harder to operate clutch and throttles that are stiff.  So, add the cost of shortened cables to your bar change.  And expect to modify the steering stops to prevent tank contact.

2. I have not ridden a motorcycle since this '78 in many years and I feel that it is a bit sluggish.  And, a cold head pipe will tell you volumes.  I'd like to do a few things to speed it up some.  Right now it is 100% stock AFAIK.

Check the head pipes for even heat.  A four cylinder engine running on three is indeed sluggish.  Your bike should do accelerate from a standing start to 1/4 mile in about 14 seconds.  If this is not sufficient for you, then you picked the wrong bike or you are going to spend a bit of money on engine parts to improve power.  Got an extra $1000-$2000 to distribute?

Another really good clue as to how well your engine is running, is to look at the combustion deposits on the spark plugs.  At minimum, they should all have the same pattern of deposit.  If one shows different deposits than the others, surely something needs attention.

3. Any concerns removing the crash bars? (other than the obvious)  The bars on my bike are rusty and ugly and I'm not one to drop the bike (unless someone decides to hit me).   I'd also imagine it would help out an itty bit on power removing that extra weight.

 
Try 0000 steel wool on the rusty chrome.  It amazing how well that works.  The crash bars will save the engine cases and maybe your leg in an accident.  Oil, water, sand on the roadway can happen anytime.  There are those that have been down and those that will be.  Crash bars can mean the difference between riding home or towing home.  If you are a new rider, you might rather remove the bars after they been scraped up, instead of replacing alternators, points covers and ignition bits.

4. The choke/idle is iffy.  Bike takes too long to warm up- maybe 10-15 minutes before idle goes to normal (80-90 degree days).  Not sure if this is an easy diagnosis or not.  The bike is almost sketchy to drive if i'm riding from a cold start (lurching forward, etc).  Maybe this is just the way it is but thats what I want to know

You should be able to drive the bike when cold by leaving some choke on.  It's gonna idle high while the choke is on, but it still be driveable.  The choke should come off in increments while riding, and when it's completely off should idle at about 1050 RPM.

5. I am using 94 octane in the tank.  The dealer told me to put in some sort of additive.  Is this necessary or will it help, or...

In the US, 87 pump rating gas is all you need.  The bike's compression ratio is only about 9:1.  Higher grade fuels are a waste of money for the buyer.  I don't know why you would need an additive.  You don't need a lead substitute, cause aluminum heads have steel valve seats.  If your carbs are dirty, maybe an additive like seafoam can help.  But, only if it is not severe.  If you have a cold head pipe, a slow jet is likely plugged and without flow, an additive isn't going to clear the passage.

6. The motorcycle dealer I got the bike from told me a few things I just want to make sure of as I'm an itty bit suspicious.  He told me I had to start the bike every single day no matter what and run it or else "it may not start again".  he said this will also happen if I don't turn off the fuel after every ride.  he said I'd probably have to bleed the carbs if I don't turn the fuel off after every ride.  He was extremely insistent that the bike wasn't going to run right otherwise.  He countered everything I said with "dude, its 30 years old, what do you expect?".   I'd prefer to fix these things if possible ...its no sweat turning off the fuel line but...I'd rather not if I can address the problem.  I also don't want to bleed the carbs everytime I forget.

There is no doubt these machine like regular operation to run their best.  Fuel is a solvent, too.  And running this through the carbs keeps them clean.
However, fuel evaporates and the cabs are vented to the atmosphere.  When the bike sits, fuel evaporation leaves behind varnish like deposits.   As the pilot jets are only 0.016 inch in diameter,  it doesn't take much of a deposit to effect their operational flow, and cause the engine to run badly.
Another consideration is how clean the tank is and the integrity of the fuel filter.  If small particles get lodged between the float valve and the valve seat the carbs will overflow.  To thwart this, turning the petcock off whenever you're not riding can save finding gas puddles on the garage floor, or the engine crankcase filling up with gasoline.

Cheers,

[Porscheguy912]

I'll take the crash bars, don't care what they look like.

HA!

Did my little episode frighten you? 

[ilovemy78]

You folks are bad ass.  Straight bad ass.

Ok, so...

I guess I'll go from new to old cause the thread is easier to read that way:)

Bars- What I did with my old SR500 (to the previous poster, yes a kick ass single!) was literally loosen the bolts and turn the bars down.  I was thinking of doing the same with the CB750.  No immediate plans to buy cafe style bars or whatever.  To another poster yes, I need to take into consideration the cables- seems to me the best way is to turn the bars and then see what adjustements/replacements need to be made.  So the question is, is is stupid to just turn the bars and drop them?  Maybe thats more of an opinion but I guess what I'm getting at is I don't want to sacrifice turning radius or center of balance, etc...

Twotired you have my head spinning- I understand about half of what you said So give me some time to Google all that.  I got the steel wool immediately after your suggestion (could only find 00) and the rest except on the exhaust (bars?) went away immediately.  Thanks! 

I removed the crash bars.  I know they are helpful when you spill but..well...thats on me I guess (I'm not a new rider, but I haven't been on a bike in a while since this one).  I hear there are less ugly ones, maybe I'll check those out.  I also removed some aftermarket cargo thing that was mounted OVER the back of the seat which was pretty stupid because you can't get to the battery without removing it...

Well, once again the dealer told me to put the highest octane I could in the bike.  So thats what I did.   I was generally disappointed in this dealer and whats worse is that he is the #1 used bike dealer in the entire metro area.  I suppose in his defense he doesn't spend much time working on 30 year old bikes, looked like mostly harleys and british bikes.  Ok so 87 octane next fill up.  I wonder if that has anything to do with the idle being so high for so long....?

The bike (in theory) has been fully tuned in the last month.  Has a new battery (this I am sure of), new jets, needles, etc (at least thats what the dealer said), carbs cleaned, and the dealer said the tank (surprisingly) was clean, no rust, didn't need any work. 

In Re- power.  The bike is great and has good power.  But for some reason, and I'm coming from where I wasn't riding anything faster beforehand, I feel that bike is a little sluggish.  The bike sounds and feels fantastic, it just doesn't have the kick I had imagined.  I'll run a 1/4 mile and see what I get and reply back.  Maybe I've gained too much weight from all the beer since the last bike...hmm

Idle- Is this bike supposed to be a real jerk to me when i'm warming it up?  Right now if its cold and choke is out the bike vascilates from 3-5k rpm.  It has this thing where the choke is either all the way out (3-4k rpm) or down to like 1500rpm.   When driving and coming up to stop signs/lights/etc the bike can get really sketchy with the idle so high...Maybe thats something I just need to get used to while its cold...Also switching gears while its cold feels very rough....this could all be normal, just checking   I will take everyones advice and ride the bike more.  Like twist my arm!

So where am I with the fuel tap?  On/off, or I decide?  Do it when I remember?  Do it when stored for a long period?

I have a severely cracked oil cover (the cool "750four" lettering) and pieces are missing on it so I may have to try to buy another one.

I'm sure my terminology is all screwed up but it'll iron itself out.

I really love this bike no matter what. Guess they call that unconditional love, but that starts to sound a bit freakish.

Fotos:






Comments? 




Thanks again.

[medic09]

1.  Look up everything TT says that you don't know about.  Or ask him.  He's one of your best resources here.  You'll find the others as you go along. 

2.  The pics look good.  Congrats on a good score!  It sounds like it will take just a little while to get it all sorted.  See item #1.

3.  Those handlebars look like mine.  A little taller than stock.  I like mine because I like to sit up and back.  I think turning those down would be pretty drastic.  Then, of course, there's the scientific method.  Try it.  You'll soon see for yourself.  Little is irreversible as long as you don't cut or alter anything.

4.  There are fairly subtle case guards that you can get for our bikes if you look around.  I'm guessing what you took off is one of those big ugly things that bolt onto the front of the downframe.  I sympathize.

5.  Sound like you do want to address that idle.  I'll let someone else address that as I've got to run.

Welcome!

[gold72]

Question
So where am I with the fuel tap?  On/off, or I decide?  Do it when I remember?  Do it when stored for a long period?

Answer
Just make a habit of shutting it off when you park the bike, it will become second nature

By the way listen to what Two Tired has to say, his advice is priceless

good luck and nice looking ride!

[ilovemy78]

Thanks folks.

Any way to get that rust off as seen in the fotos?

The wool won't do it.

[UnCrash]

Hi Mate,

I have the same bike.  It's currently stripped down to the frame ready for paint.

I can tell you that your bike is not in good tune because when it is it pulls hard all the way up to 120+ mph.

A couple things sound like they may be off, as they were on my bike.

The points and timing may be off, affecting your cold start issues negatively.  The better shape the points are in, and the better it is timed, the better the fuel burn. 

Your dealer at best is misinformed, and at worst is a liar.  I wouldn't personally trust all the information received (new needles etc/) seeing how some of it was absolutely incorrect.

My recommendations:

Download a manual (more info in this thread) ---> http://forums.sohc4.net/index.php?topic=30639.0

When you have it running and warmed up, spray some brake cleaner (auto parts store purchase) on the carbureator intake boots right near the engine in a methodical, boot by boot way.  If the idle picks up on a particular boot you know that there is air leaking by.  Please review a previous thread of mine where I describe this phenomenon, how to test for it, and the solution (buy new ones) ----> http://forums.sohc4.net/index.php?topic=35185.0

Check the points and the timing.  This is pretty easy to do, here's a great post on how to do it with a sheet of paper    ---> http://forums.sohc4.net/index.php?topic=5752.0

These bikes are actually fun to work on (if you like that sort of thing)  I hope you do because while Hondas are relatively bullet proof when in good running sorted out order, it may take a little work to get them there --- especially with wacky dealers.

Best of luck,

You're welcome to PM me with any direct questions.

[gsgleason]

Finally I have something to contribute: you can get 0000 steel wool at home depot.  It's also useful for polishing dirty frets and fingerboards on guitars.

That bike looks very clean.  A guy in my area is trying to sell that same bike with 18k miles for $3k.

Is it me or do the handlebars look like slightly different angles from the top view?

[medic09]

Is it me or do the handlebars look like slightly different angles from the top view?

I think they are higher aftermarket bars.  In the photo they look similar to the bars on my K8.

[MacM2010]

I'll take the crash bars, don't care what they look like.

HA!

Did my little episode frighten you? 

Maybe a little...

[dusterdude]

what part of va are you in?if you are near richmond let me know

[ilovemy78]

I'm way up at near the border of West VA.....

A bit of a drive

[ilovemy78]

Is it me or do the handlebars look like slightly different angles from the top view?

I think they are higher aftermarket bars.  In the photo they look similar to the bars on my K8.

So you don't think those bars on my bike are orig?  interesting.

[medic09]

Is it me or do the handlebars look like slightly different angles from the top view?

I think they are higher aftermarket bars.  In the photo they look similar to the bars on my K8.

So you don't think those bars on my bike are orig?  interesting.

Just my guess from the photo, as I mentioned.  There are those here who know far better than I.

[ilovemy78]

A unexpected thing happened to me while riding today.

The bike stopped.  I looked at the odometer (having been reset after my last fill up) and I only had 120 miles on the bike.  That only averages ~30mpg which I must say seems incredibly poor mileage and I absolutely did not assume I had run out of gas.

Switching to reserve I tried to restart the bike but couldn't.  The oil light was on and I couldn't get the bike out of gear into neutral.  Turns out the neutral light wasn't going on although I was successfully getting the bike was in neutral.  Not sure why that occurred.  The bike started and I cruised over to the gas station to put (87) in the tank.  The tank was bone dry and I was able to get 3.8 gallons into it (!).

I am using the bike to cruise around town and a little bit of highway but still it seems that 30mpg is really low for a bike isn't it?  I ride the bike very softly as I'm still getting used to it..

As mentioned earlier in this thread, the bike was tuned up, new filters, etc just a month ago.  Well, in theory.  I wouldn't know any better right now.

[UnCrash]

My 78F gets 45 to 50 depending on how much I flog it.  I have the stock airbox, foam filter, and factory spec jetting.

Yours should do better.

What do your plugs look like?

[super pasty white guy]

With that mileage, it sounds like you'll save a bunch of time if you spend a couple of days doing a carb clean and a tune-up.  You don't know if it was done right unless you've looked yourself.  It won't cost you much more than time and then you'll really know what's going on.  You might also want to check and make sure that you don't have a dragging brake as well.

The shop manual is invaluable and will walk you through the jobs (as will this forum).

spwg

[ilovemy78]

Yeah I guess I'll have to "dive in".  I'm not a mechanic (by any means) and so this is going to be a challenge for me.  I will do some homework and report results.  Although I would be truly unhappy if I found out that this (big) d.c. area dealer did not do what they said they do (carb clean, new needles, new plugs, filters, oil change, etc)...but that would be the mystery of life, wouldn't it...

I must say the idle is the worst part still...

what I really need is to convince a gear head in my area, feed them beer and food and let them do magic while I learn.

right now I don't have a single bike shop that is closer than 40 miles....

thanks again...will break out the manual some more and deep dive.

Maybe i'll make space in the garage for a little while..rainy day here in d.c.

[medic09]

You'll be a amazed what you can do with this bike with some patience, persistence, and questions!  I am one of the members who is dumb as the day is long with most things mechanical.  With the help here I took a bike that got about 25 mpg, with all sorts of electrical stuff that didn't work, and got to work.  Everything electric now works, though I couldn't reproduce the results alone.    I get mpg in the 42 range at highway speeds, and a recent relaxed Sunday on backroads got me 50 mpg.  My bike is not pretty, but it runs reliably.  I've put on thousands of miles doing everything one does with a motor vehicle.

You've already seen the good will and knowledge here.  Go slowly enough to remember to ask questions, and you'll do well.

Dealers often mean different things than owners with the same words.  'Carb clean' to me meant completely tearing down, cleaning, and rebuilding my bike's carbs.  Dealers often mean 'remove the bowls, briefly  spray or soak, and reinstall'.  They will often use cheaper quality materials than we do.  They often don't think older bikes (which many of them aren't really familiar with) are worth their time and thorough attention, plus they would have to take time to learn too much.  Not all, mind you; but I think it isn't uncommon.

[ilovemy78]

Ok well I did a little work on the bike today and a test or two.

Re-adjusted the idle as it was idling high again after setting it to 1100 about a month ago.

Checked for leaks in the carb boots.  Idled solid @ 1100 except for #4 where it went up (maybe) 50rpm for a little bit.  I'm assuming the boots are ok from these results.

Checked all fluids, seemed as spec in the manual.

Refilled the tank with 87.

Unsuccessfully tried to adjust the choke knob so that it wouldn't fall down (right now it either sticks open or closed but will rest nowhere in between). 

Poured about 8 oz of Seafoam into the gas tank.  Seems like I have a lot of options with Seafoam but not sure which other ones I should do next (if any).

Bike seems to be running pretty smooth for the time being.  One irritant is that I am beginning to think there is a fuel line issue as when the bike is idle @ 1100 if I crank the throttle (instead of very slowly turning it) the bike will fall off and stall if I hold it.  If I let go quick enough the bike won't stall.  It's not a total problem but might as well try to fix it.   

I haven't done a 1/4 mile yet but I am pretty confident it will do it in 14 seconds. 

Based on the repair order from my dealer he did a "carb clean & sync".   I guess I won't know exactly how good the carbs look until I take them apart.

I haven't checked the plugs yet as i don't have the tools for it yet.  But that's on my list.

Thanks