Topic: ENGINE HOSED(???)

[Jerry Rxman Griffin aka MuthaF'er]

Terry, terry, terry,

I know you've been waiting for me to come along  You know good and well the F(ugly as you refer to it) was brought out for Honda to try to hold on to sales until the DOHC came out. The HP and performance were increased over those anemic mid year K's through those various mentioned means. I had 2 buddies with 500 Kaw triple smokers that went around picking on those mid year K's just to embarass them. They tried to pull that #$%* on my F(ugly)but both got seriously embarassed by mine after only 3rd gear and had to shut the hell up afterwards. The F2/F3 was hoped to be another improvement that just didn't cut the mustard vs the 900Z's. Closer but no cigar. Too bad it took Honda so long to bring out the DOHC lineup.

[Terry in Australia]

Terry, terry, terry,

I know you've been waiting for me to come along  You know good and well the F(ugly as you refer to it) was brought out for Honda to try to hold on to sales until the DOHC came out. The HP and performance were increased over those anemic mid year K's through those various mentioned means. I had 2 buddies with 500 Kaw triple smokers that went around picking on those mid year K's just to embarass them. They tried to pull that #$%* on my F(ugly)but both got seriously embarassed by mine after only 3rd gear and had to shut the hell up afterwards. The F2/F3 was hoped to be another improvement that just didn't cut the mustard vs the 900Z's. Closer but no cigar. Too bad it took Honda so long to bring out the DOHC lineup.

Ha ha, I bought a shiny new F0 ("Farking 'Orrible") in 1978 Jerry, the Honda dealership couldn't sell them because no-one wanted one (including me, but the F2 was 300 bucks dearer, so I took what I could get) and they had several of these red-headed stepsons sitting in crates in their warehouse for several years.

It was the fetching "Chicken Yellow" color, and as much as I wanted to love it, I couldn't. It was slab sided, top heavy, handled like a pig and that bulbous muffler would touch down every time I tried to lean to the right, so I tried to plan my routes so that most of the corners I went around were lefts. On the one occasion that I forgot about this handicap, while chasing my mate Peter on his old Suzuki 500 Cobra thru a set of "S" bends, that useless fcuking muffler dug in and threw me down the road! Wonderful...........

And don't get me going about the useless brakes, the front single pot caliper was weak, and the rear dual opposed piston caliper, with twice the braking power of the front brake would lock with the slightest pressure, once again, throwing the unwary rider down the road again. what a POS! 

So, the "F-ugly" was a slab sided, top heavy, poor handling, dangerous POS. But was it faster than the K's? No. In my experience, it wasn't any faster, and Peter and his brother Davey had no problems keeping up on their K2's. I did have a drag race against a Kawasaki Z1, but it kicked my arse too. I'm glad that you beat those Kawasaki 500 pilots though mate, I'd be surprised if you didn't with a 50% capacity advantage? Cheers, Terry.  

[AbbyRider]

My vote would be to pay the $650 and swap the motor. I don't think any of the Honda mechanics around here would do it for that amount.

And it's too funny that the original question evolved into a debate about K1 vs K5 power.

[750K]

Haha, cheers to you Terry. I always enjoy your posts. I agree with AbbyRider, get a running motor in there and enjoy the spring summer season. Rebuild the current motor when you have the time.

[longshanks]

$650 is for a "core charge" for my old K6 engine swapped for a rebuilt K1. I don't believe that includes labor either. What's a fair price to pay?

Not to stir the pot but here is a quote from Hondaman on a previous thread of mine. No mention of 10hp of course but that figure came from the "Thoughts of Hondaman" thread. Besides 10hp is a figure based on averages, and I'm sure everyone can attest that every bike is different and has its own character.

http://forums.sohc4.net/index.php?topic=104683.msg1171673#msg1171673

There's a pretty long list of things between the K0 and K6 that made the later bikes less powerful. A few things are on the outside, but most are inside the engine. The biggest things are the cam changes, port changes, spark advancer changes, rocker arm shafts, final drive bearing, compression ratio, airbox changes, and then the jetting, to match it all and make the plugs stop fouling. This is why so many folks have tried to simply install 120 mainjets from the K0, only to find fouled plugs, while others have installed K0/K1 top ends on the later bikes to increase their power output. This is the topic of the Performance chapters in my book for the 750. Most of the things can be done once inside, but it is an inside job, so to speak...

[Duke McDukiedook]

Oh, I thought 650 included the labor. Find a running used engine and put it in yourself.

[Stev-o]

Oh, I thought 650 included the labor. Find a running used engine and put it in yourself.

+1

[longshanks]

Here's a video taken of the bike idling. Noise is VERY pronounced when its cold and its really hard to keep it running while cold since I had work done on it. I don't think he dunked the carbs in cleaner or set the floats to 26mm(just eyeballed it) Pretty sure it just changed the jets and synced the carbs. Does it sound like a cam chain rattling around in there? Also is it normal to have small metal shavings in the oil pan?

IMG_1296.MOV

I took it to a Honda motorcycle dealer and the mechanic came out with his laser thermometer and cylinder 1 and 2 were around 400 and 3 and 4 200. He was saying the carbs were out of sync causing the slapping sounds blah blah, etc. I nodded like I didn't know anything and just let him fire away 
He very may be right though, I suspect the carbs have gone out of sync since it was worked on. I have been playing with the air screws in 1/4 turns to try and get rid of the backfiring on it but does that mess up the synchronization? From what you guys can tell from the video does it sound like a cam chain tensioner out of adjustment, bad cam chain, or are my rod bearings toast?

I suspect it might be entirely a carb issue causing a rough idle,(especially when cold), and a sloppy cam chain.

[dave500]

ill bet the carbs were never synced?your airscrews wont affect the sync,is the ignition spot on?done by the shop?

[dhall57]

How was your 750 running before taking it in to this local shop? Is this when all your trouble started? Having metal shavings in pan is never good. How many miles is on your bike? Do you know any history on it. PO could have had some engine work done in years past and just didn't clean up very good leaving trash in pan.
If haven't adjusted cam chain, do that and see if that helps.
+ 1 to what Dave is saying.

[Duke McDukiedook]

Here we go- do a full tune up including cam chain tensioner- YOURSELF. Make sure you are getting fuel and spark where you need it, confirm timing.
Look at the carbs dead last.

Then you will know a little more about your situation.

[Jerry Rxman Griffin aka MuthaF'er]

+1 but don't just "look" at the carbs - do a real sync after a real tune up. These are the "minor" necessary things to do BEFORE worrying about pulling an engine and opening it up. If someone can't do these things they don't need to be opening an engine up.

We'll assume it was in neutral. How does it sounds when you pull in the clutch lever?

Work HAS been done to the engine. I first thought you may have a 77/78 F until I saw the spokes and the carbs. That engine was in all likelihood off the bike when it got painted and it was probably off the bike to have some internal work done.

 

[longshanks]

Bike was running way worse before i had work done on it. Lots of low end mid range hesitation. Discovered it was way too rich and dropped the mains to 115 from 120. However whats worse now is its way noisier(i believe its the cam chain) and very very hard to keep it idling when cold.

That was the first time the pan had been dropped since I owned the bike but I thought small metal shavings were somewhat normal for these bikes after time. The bike has 26k and 120psi on all cylinders so it's a little tired. Valves, points were adjusted 6 months ago and I just replaced the plug caps since the old ones were measuring 10-12k ohms and varied from each other a lot. Also have brand new ngk plugs too. My guess is that it ran great for the first 50 miles than the plugs got dirty. I'll pull them to confirm.

Two important things the mechanic didn't do was clean or dunk the carbs and didn't measure float height, just a quick eyeball check. If not all float heights are at 26mm will that cause certain cylinders to be richer/cooler?

Also can the carbs throw themselves out of sync? Can the nuts on the top loosen?

[754]

 Sounds like your motor may be OK..no metal at all in the pan means it may have been off and cleaned before.
 It early in the season, you got time to work it out.. a member on here does carbs cheap, if you cant.
 

[longshanks]

UPDATE:

So I went out to start the bike today and it was stumbling hard like it was running on 3 cylinders but would smooth out if I revved it to 3k rpm. Naturally I pulled the plugs and this is what I've found. No.1 is fouled with gas and the rest are a pretty nice brown color with No.4 being a little black near the threads. As soon as I pulled No.1 I could smell gas strongly and could actually see that it was wet. I checked the spark as well by holding the plugs to the head and cranking over--everything seemed fine and I was getting a nice blue spark.



I also "dynamically" set the cam chain while it was running and I could start to hear it "whir" so I turned it off and set it again statically using the methods stated in the manual. Started it right up and the "whir" was gone so I think I've eliminated the possibility of a worn/loose cam chain making the noise. I'm feeling like it really could be bad rod bearings as the sound seems to emanate from the crank. Either that or the carbs are so completely out of sync their causing that clacking noise.

I checked all the float bowls as well. Below are my rough estimates on how "full" they were of gas.

No.1 80%
No.2 70%
No.3 60%
No.4 40%

Now I need to set the valves and check the timing even though he assured me the timing was on. After that I suppose I'll send the carbs to Digger and have him rebuild and clean them. I'm just hesitant if I do that then find out the noise is still there after syncing the carbs then I'm out money but I guess at least I'll have a set of ready-to-go carbs. 

Is there any other way to check to see if the rods or rod bearings are bad? Maybe I'll post another video of the bike starting up from a dead cold as the noise is way louder when cold. Isn't it rare for the rod bearings to go out on these bikes? Also for the No.1 plug how do I determine if its oil as well and not just gas?

[scottly]

Here's a video taken of the bike idling. Noise is VERY pronounced when its cold and its really hard to keep it running while cold since I had work done on it. I don't think he dunked the carbs in cleaner or set the floats to 26mm(just eyeballed it) Pretty sure it just changed the jets and synced the carbs. Does it sound like a cam chain rattling around in there? Also is it normal to have small metal shavings in the oil pan?

IMG_1296.MOV

I took it to a Honda motorcycle dealer and the mechanic came out with his laser thermometer and cylinder 1 and 2 were around 400 and 3 and 4 200. He was saying the carbs were out of sync causing the slapping sounds blah blah, etc. I nodded like I didn't know anything and just let him fire away 
He very may be right though, I suspect the carbs have gone out of sync since it was worked on. I have been playing with the air screws in 1/4 turns to try and get rid of the backfiring on it but does that mess up the synchronization? From what you guys can tell from the video does it sound like a cam chain tensioner out of adjustment, bad cam chain, or are my rod bearings toast?

I suspect it might be entirely a carb issue causing a rough idle,(especially when cold), and a sloppy cam chain.

Sounds like the infamous CB750 clutch rattle-with-bad-sync/one dead cylinder syndrome to me. Check your float bowl levels with the "clear-tube" method. Your "80%" plus the fouled number 1 plug point straight to the number 1 carb. Don't be too quick to assume you need to rebuild the motor.  

[Stev-o]

#1 could be fouled, buy new plugs and caps, trim wires .25".
Also sounds like floats need to be set, and carbs sync'd.
Change thread name to maybe not hosed!

[longshanks]

Here's a video taken of the bike idling. Noise is VERY pronounced when its cold and its really hard to keep it running while cold since I had work done on it. I don't think he dunked the carbs in cleaner or set the floats to 26mm(just eyeballed it) Pretty sure it just changed the jets and synced the carbs. Does it sound like a cam chain rattling around in there? Also is it normal to have small metal shavings in the oil pan?

IMG_1296.MOV

I took it to a Honda motorcycle dealer and the mechanic came out with his laser thermometer and cylinder 1 and 2 were around 400 and 3 and 4 200. He was saying the carbs were out of sync causing the slapping sounds blah blah, etc. I nodded like I didn't know anything and just let him fire away 
He very may be right though, I suspect the carbs have gone out of sync since it was worked on. I have been playing with the air screws in 1/4 turns to try and get rid of the backfiring on it but does that mess up the synchronization? From what you guys can tell from the video does it sound like a cam chain tensioner out of adjustment, bad cam chain, or are my rod bearings toast?

I suspect it might be entirely a carb issue causing a rough idle,(especially when cold), and a sloppy cam chain.

Sounds like the infamous CB750 clutch rattle-with-bad-sync/one dead cylinder syndrome to me. Check your float bowl levels with the "clear-tube" method. Your "80%" plus the fouled number 1 plug point straight to the number 1 carb. Don't be too quick to assume you need to rebuild the motor.

The noise doesn't go away when I pull the clutch in and it still is there even when all cylinders are firing. Once it warms up all are firing and the idling smoothes out but the clacking doesn't go away.

Don't all float bowls need to be around 80%? In any case it sounds like the bowl is filling up too quickly and dumping too much fuel in No.1 yes?

[longshanks]

#1 could be fouled, buy new plugs and caps, trim wires .25".
Also sounds like floats need to be set, and carbs sync'd.
Change thread name to maybe not hosed!

Those are new plugs and caps, only 300 miles on them!   Wires were not trimmed but I may consider re-wiring since the insulation on a couple wires is getting brittle and wearing.

Carbs were synced by the mechanic working on my bike but I noticed after 20 minutes or so after riding it home I felt hesitation and a bit of blubbering which was very likely No.1 starting to foul the new plug. I plan on setting the floats, check timing, adjust the valves, and then a final carb sync but I suspect I may have to have them cleaned and rebuilt by SOHC Digger since there was rust sediment in the bowls before I had all this work done on it.(not too much) It's likely something is clogged or worn out of spec.

[longshanks]

Ok, so I've done a bit of work to it again. This time I cleaned up the ignition connections since they were corroded and dirty and now the all the cylinders run at the same temp. Set the valves, check and set the points, timing, double checked the cam chain adjustment, set the floats, dropped the jets to 110 and synced the carbs. Bike runs smooth and has good power but the clacking noise is still there, especially when cold. However if I rev the motor up a bit or when its nice and hot, the noise is much quieter.

What's going on here?  Too much slack in the primary chain? stretched? worn out?

[Stev-o]

Did you sync the carbs?

[lucky]

The worst has happened!     The mechanic working on my bike after starting it up heard a clacking noise coming from the case. After dropping the oil pan he found some metal shavings, some steel, some aluminum. I'll go and listen to it tomorrow and if it sounds the same then all along I was thinking it was a noisy cam chain when in fact it could have been a worn rod bearing.

I'm so bummed I can't even express it. I just put hundreds of dollars into it. New steering head bearings, new tires, new fork seals, clutches and clutch cable, carb rebuild, carb boots, starter motor, spark plugs and caps, etc. All of it was gearing up to go on a long cruise with my brother and now I'll have an expensive brick sitting in my garage

I'll try and take some video of it running tomorrow and perhaps you guys can help me diagnose it. If it's truly a goner engine should I look for a used one or get ambitious and open up the whole engine and rebuild? I always planned on going to 836 and getting some head work done on it. I'm pretty broke now so it all seems so far off.

Did the mechanic show you the metal filings???
Did you see it as it the pan was removed??
I just don't like this story.
Mechanic has a lot of bikes etc.,.
Eye balled the float levels etc.,.

I would NOT run that engine!
I would take the engine out.
Turn it upside down and remove the bottom of the case.
That way you can check the big end bearings without taking the entire engine apart.
You can also check for any other damage.

[KC_Northstar]

"so unless someone can show you a dyno card, it's just an opinion. Cheers, Terry"

How about the dyno runs that Hondaman did in the 70's???

in his posting titled "the cb750 HP thieves over the years..."  he says:

I tested one of my friends KO bikes at 65 rear wheel HP, at over 30K miles on the ticker.  The last K4 I tested (1974 I think)
was about 40 HP on the ground at about 8K miles.  All tests were on the same "truck Dyno", an in the floor type of rear-wheel dyno used for checking out diesel trucks near Macomb, Il.

And my personal experience:
during the 70's I spent alot of time at the local drag strip.  I had a stock K1.  A guy with a stock K0 consistently ran
about half a second faster than me and another stock k2 was about 3 tenths slower.
As the 70's slowly went by I could see the CB750's slowly losing power and performance when it came to quarter mile performance.  The last CB750 I ran down the quarter mile was a friends K5 which ran a 13.89 - about 7 tenths slower than
my K1.  I remember that bike just plain running out of steam on the top end.

KC

[longshanks]

Did you sync the carbs?

yes

[longshanks]

Did the mechanic show you the metal filings???
Did you see it as it the pan was removed??
I just don't like this story.
Mechanic has a lot of bikes etc.,.
Eye balled the float levels etc.,.

I would NOT run that engine!
I would take the engine out.
Turn it upside down and remove the bottom of the case.
That way you can check the big end bearings without taking the entire engine apart.
You can also check for any other damage.

Yes he showed me the metal filings but I did not see him drop the pan. I know some things may sound off but I do trust the guy and have worked on the bike with him before. He's a lifetime enthusiast like many of us here and has always been extremely fair with labor prices.

As far as rod bearings are concerned, I hear that they are very very unlikely to go bad(this was confirmed by Hondaman to me through email) and other members on this forum have attested to this as well. If I remove the bottom of the case wouldn't that be the same as splitting it?