Topic: My first complete build 72 CB750 - completed for now...

[algophobe]

Yes fouling from excess fuel or oil.
If the oil was getting in from the rings; That would likely effect the compression (unless it was swimming on oil) But if it's coming from a valve guide, that would not effect the compression.
If it is from fuel; Then I would not say the fuel itself, but an excess of fuel that is coming from that #2 Carb. (possibly a float needle not seating properly?)

the spark plug do look wet and black like an oil foul, but then all the sparks looks like that, and yet the other three runs still. the piston definitely not swimming in it. however if its coming from the valve guides, what can you do? these were new valve guides as the head was redone with Kibblewhite guides. the repair manual suggests running hotter spark plugs which doesn't seem to make sense to me. currently using NGK iridium IX plugs. you think running heavier weight oil would help?

I also check the needle, on the CR specials you can take the top off and pull the needle, there is retention clip that was slightly off... I thought that this may be the cause, but one other carb had the same situation as well and its running fine. i'll post some pics later and show you that I was referring to.

[Terry in Australia]

Hey mate, just for a test, ditch those Iridium plugs and try some NGK D7EA's. I've got a set of Iridiums in my garage that I yanked out because they made my bike run like sh1t, I can't explain why, they were the right ones for my bike, but ditching them and replacing them with the D7EA's (also recommended by Hondaman) was like night and day on my bike. I remember Mike Reick had the same issue. I'm sure I'll be shouted down, but for the sake of a few bucks, just give it a try, and report back? Cheers, Terry.

[Godffery]

Yes fouling from excess fuel or oil.
If the oil was getting in from the rings; That would likely effect the compression (unless it was swimming on oil) But if it's coming from a valve guide, that would not effect the compression.
If it is from fuel; Then I would not say the fuel itself, but an excess of fuel that is coming from that #2 Carb. (possibly a float needle not seating properly?)

the spark plug do look wet and black like an oil foul, but then all the sparks looks like that, and yet the other three runs still. the piston definitely not swimming in it. however if its coming from the valve guides, what can you do? these were new valve guides as the head was redone with Kibblewhite guides. the repair manual suggests running hotter spark plugs which doesn't seem to make sense to me. currently using NGK iridium IX plugs. you think running heavier weight oil would help?

I also check the needle, on the CR specials you can take the top off and pull the needle, there is retention clip that was slightly off... I thought that this may be the cause, but one other carb had the same situation as well and its running fine. i'll post some pics later and show you that I was referring to.

It is possible that one of those guides was damaged or didn't seat properly during installation.  That requires dissemble to check, so I would look at all other potential issues B4 that.   

As for the Float needle; that is at the bottom of the Carb. The needle you described up top is the slide needle.

[algophobe]

thanks for the input gents, I thought about changing the sparks as well. supposedly the iridiums are "more resistant to fouling out".  i'll put that on my list of things to do before any dismantling.  was thinking of draining the oil and see if there is any strange metal shavings that could indicated something going wrong on the bottom end that would push me to pull the engine. if no improvement, then i'll probably be taking down the carburetor once again after that and check the float needle as suggested. then go from there to check the head and work downwards.

just curious, when you're hand cranking the crank, should there be somewhat of variations resistance? I know there is some difference depending on the location of the piston, but I do notice some spots that are "rubbery" (for a lack of a better word).

[Terry in Australia]

Yes mate, it gets "rubbery" as the piston is traveling up the cylinder compressing the fuel/air mix, so one complete turn of the crank will feel easy, the next will have a lot more resistance.

[algophobe]

Yes mate, it gets "rubbery" as the piston is traveling up the cylinder compressing the fuel/air mix, so one complete turn of the crank will feel easy, the next will have a lot more resistance.

yes I sound like a total dumbass  but you can read and watch all you want but hands on experience to feel, see, and hear what "normal" is supposed to be like only comes with doing it yourself I guess. once you know normal then you can kind of develop your antennae for what is "abnormal".  I've never actually heard one of these cb750 run in person, some of these extraneous noises freaks me out. like hearing a dry clutch in person for the first time. one can only hope to have a knowledgeable friend near by to learn from... till then, you all will have to put up with stupid questions.

[Terry in Australia]

That's OK mate, we were all dumbasses once, but that's OK, you've gotta start somewhere! Cheers, Terry.

[algophobe]

well, some parts came in. I ran her yesterday with the hotter new spark plugs D7EA using the velocity stacks that came with the Keihin Carbs just to see how it runs. I drained the oil and put in 20w50 (since california gets hot these days anyways). all four cylinders fire like a champ. but we'll see if it fouls out today again.

I've order four of the K&N RC-1820 pod filters as Godfrey suggested from Bikebandit. apparently there is a shortage and is on back order. they were only able to ship 2 and the order automatically cancels after 28 days. does anyone have any supplier for these things? i'm using the 51 mm ID filters. just need to more to complete the set.

[Terry in Australia]

I'm glad you're trying the D7's mate, I'll be surprised if you foul a plug. Ebay is full of listings for those filters, but I wouldn't know if they're cheaper or more expensive than BB. Cheers, Terry.

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050890.m570.l1313.TR0.TRC0.H0.TRS4&_nkw=K%26N+RC-1820&_sacat=6000

[algophobe]

Well terry.. fine advice u gave all the way from over there. The D7 have consistently fired and was able to time the engine to +10 for a fraction of the cost! New pod filters placed... turns out K&N's manufacturing plant is near my work in Riverside California. They had like 20 something on hand and we weren't able to figure out why Bike Bandit couldn't stock it. Pretty much the same price and was able to get it to my door in 24 hours. My plans for this weekend is to take out the spark plugs and check to see how they actually look and balance the carbs.

[algophobe]

I balanced the carbs using this old motion pro mercury gauge I've acquired many years ago. the throttle response seemed snappy and crisp as one would want to have, the rpm quickly return to idle when throttle is released. I proceed to disconnect the vacuum lines to the mercury gauge and re-run the engine. I notice now that when I rev the engine to by about 1/4 turn it doesn't snap back to idle as crisp as it did during the balancing process with the gauge hoses on. the engine only gradually returns to idle when the throttle is release, is this an issue of carb balance or air/fuel mixture in general? I find that the Keihin CR specials, the air screw for 1/2 turns out, anymore or less it would sputter and shut off. I've looked various sources on carb balancing and tuning, nothing really mentions this problem.

[Terry in Australia]

How well sealed are your home made vacuum teats mate? If its sucking air you'll have those symptoms.

[algophobe]

How well sealed are your home made vacuum teats mate? If its sucking air you'll have those symptoms.

its pretty well seated, with gasket makers as well. but it could be due to the rubber caps that comes with the "teats", they may be a little thin and loose.. i'll try and put thicker ones and see. the tubing from the synchronizing gauge is thicker so that may be why I didn't notice it during balancing/testing. so that sluggish return to idle after throttle opening is due to vacuum leak from the engine side of the carbs?

[Terry in Australia]

Well it could be mate, it's a common symptom of a vacuum leak.

[algophobe]

as one of the final issues, I've been working on the paint scheme. going for something a little classic, but slightly different. what do you all think? I borrowed the idea form an Italian modern cafe design

[algophobe]

can't seem to decide on the yellow or red scheme. no flakes, just solid colors. the grey would be a solid grey, much like what you see on Toyota tundras, it a sort of fluorescent yellow.

[slikwilli420]

I like the red better, with the Honda logo. What program did you use to do that? That would be a great way to make sure you love something before painting it on.

[Godffery]

Love the classy Honda badge.
For color; have you tried red with the gray?

[algophobe]

The program is a free program called inkscape. You can download it off the web. Not exactly as seamless as Adobe Illustrator, but decent for being free. I was a graphic designer in my twenties and this was a sort of stuff that we did on a daily basis.

 I have thought about red and grey but it doesn't pop as much, in order to use red with a grayish color it would have to be somewhat of a silver iridescent color. I'll put something together and see what it looks like

[SOHC4 Cafe Racer Fan]

Opinions are like sphincters.  Everyone's got one and they all . . . .

I would not paint until YOU find something that really moves you.  You can always re-paint, but it's a PAIN in the ass.

Personally, I would not put a number on a bike, unless the number has some personal significance (lucky number, date you got divorced, whatever).  The year of the bike doesn't seem to cut it.  Just my $0.02!!  I'm also not much of a yellow bike person but some people are.

[algophobe]

I really like the red but I painted my kawi red.. as seen earlier in the thread... always gravitate towards red/white/black. so want to step away from it. I also like painting bikes colors that are atypical of their factory image (like blue for yami, green for kawi, red for Honda). I despise sanding, and have done plenty in the past, repainting IS a pain. you're right about the number though, I don't want to make it permanent. but I like the framing and set up of the number.

[MetroRedneck]

can't seem to decide on the yellow or red scheme. no flakes, just solid colors. the grey would be a solid grey, much like what you see on Toyota tundras, it a sort of fluorescent yellow.

Ducati has a killer yellow and dk gray paint scheme now.  Fighter Yellow is the color.  The frame is a darker than gunmetal gray.  Looks good.

[algophobe]

can't seem to decide on the yellow or red scheme. no flakes, just solid colors. the grey would be a solid grey, much like what you see on Toyota tundras, it a sort of fluorescent yellow.

Ducati has a killer yellow and dk gray paint scheme now.  Fighter Yellow is the color.  The frame is a darker than gunmetal gray.  Looks good.

I always wanted to paint a ducati lime green... hahaha

[Godffery]

R U think'n Gloss or like a modern flat?

 https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwi0kezu093ZAhXEVN8KHauNAFAQjRwIBg&url=http%3A%2F%2Fwww.bikeexif.com%2Fcafe-racer-cb750&psig=AOvVaw110l2DZ74WsIMkJdzIPCfl&ust=1520630405592488

[algophobe]

R U think'n Gloss or like a modern flat?

 https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwi0kezu093ZAhXEVN8KHauNAFAQjRwIBg&url=http%3A%2F%2Fwww.bikeexif.com%2Fcafe-racer-cb750&psig=AOvVaw110l2DZ74WsIMkJdzIPCfl&ust=1520630405592488

with the yellow/gray combo. I'd go with gloss basic colors of both, no metallic.
http://www.tcpglobal.com/Automotive-Paint/House-of-Kolor-Paint-Graphic-Colors-SG/
I was gonna use these bc 25 and 26 to mix the gray, then sg102, but apparently new regulations have banned the black and whites... digging for alternative with Shimrin2... shouldn't be that big of an issue.