Author Topic: First Motorcylce 1978 CB750K. Cafe Build (Read 17897 times)

TommyT · « **Reply #25 on:** September 27, 2011, 08:30:40 AM »

It's a VHT engine paint actually. SP404 Gold Flake

http://www.vhtpaint.com/products/enginemetallic/

I painted 3 coats on entire frame and everything. Then put 3 coats of clear using spraymax 2K clear. Turned out really well and pretty tough. I have a few scratches from installing engine and headers but it's easy to fill since it's an off the shelf spray paint.

TommyT · « **Reply #26 on:** October 02, 2011, 09:04:37 PM »

Finally threw some paint and clear on the tank and fender. Just got to upholster the seat and it will be pretty much wrapped up and ready for it's first ride.

Free Booter · « **Reply #27 on:** October 02, 2011, 09:08:27 PM »

DAAAAAAAAA.aaaaaammmmmmmmmmmm!!!

Nice. Lovin that point wedge rear frame hoop you welded..never seen in done like that before...very sleek. love the angles on the seat box and the tank.

TommyT · « **Reply #28 on:** October 11, 2011, 09:34:32 PM »

OK got it all assembled and it is only running on 2 cylinders until you ev to about 3000 rpm then the 2 and 4 pipes get hot and revs right up. Pulled points cover off and points on 2-4 barely open compared to other side. Gonna attempt to adjust those and check timing before syncing the carbs.

lucky · « **Reply #29 on:** October 11, 2011, 09:53:31 PM »

Quote from: TommyT on October 11, 2011, 09:34:32 PM

OK got it all assembled and it is only running on 2 cylinders until you ev to about 3000 rpm then the 2 and 4 pipes get hot and revs right up. Pulled points cover off and points on 2-4 barely open compared to other side. Gonna attempt to adjust those and check timing before syncing the carbs.

You need to check the DWELL. If the phenolic block on the points sets are worn down from rubbing on the crank cam with no grease, then the points can be gapped correctly but the dwell will be off. Thus weak or no spark. You would have to get new points sets.
Condensers can go bad too . They absorb only so many micro farads then they are no good. Those are about 22U micro farads. The value is stamped on each condenser.

TommyT · « **Reply #30 on:** October 11, 2011, 10:07:18 PM »

I'm gonna check it out with the dwell meter as well. I'm probably just going to order new points and condenser as well. Are the 77-78's different than earlier ones as well? Any advantage of ordering a complete points set with backing plate and everything or new points and condenser ok.

TommyT · « **Reply #31 on:** October 13, 2011, 02:50:55 PM »

Rode it around my shop complex a couple laps last night. feels great to finally get it riding. Still not running great, hope new points fixes that. The 1-3 points gap was almost .020 and the 2-4 gap was less than .006 my thinnest gauge. Adjusted those to .012 and it runs a lot better, but I believe timing is off as it's harder to start now. Not gonna mess with it until I get the new points in and adjusted. Also the #4 cylinder exhaust is warm but not nearly as hot as the others, has spark and fuel, any ideas there?

mrjack55 · « **Reply #32 on:** October 13, 2011, 06:10:05 PM »

Holy hell Tommy, your fast!

I think you win the fastest build award. Good job on your K8.
I guess it doesn't hurt that you have a full fabricating shop at your disposal.
Must be the off season. No racing going on?

TommyT · « **Reply #33 on:** October 13, 2011, 06:31:39 PM »

Yeah kinda of nice. Summer is Desert racing's slower season since it's well over 100 degree's at every race. so there's usually only 2 races we go to between april and october. Now it's full on busy season, finished it just in time. I also picked up a 1985 Magna 700 v4 a few weeks back that I gotta rebuild carbs on, Pretty sweet bobber, gonna keep that for friends and such to ride since I got it super cheap and won't kill me if it's dropped.

TommyT · « **Reply #34 on:** October 13, 2011, 09:05:58 PM »

OK so right now as I apply about 1/8 throttle it'll just sit and sputter and not rev up but once I go to 1/4 throttle it'll rev up ok. Once at 1/2 throttle it seems to hit a wall and when I let off it pops out the exhaust. I pulled the plugs and they are definately rich BUT they are a DPR8EA-9 plug so I check resistance in cap and it's right around 5K. SO i'm gonna swap out to D8ea plugs and see if that helps my cause, seems to have weak spark right now.

TommyT · « **Reply #35 on:** October 16, 2011, 09:51:29 PM »

Changed, plugs, caps, points, cleaned carbs again and drained out BRAND NEW GAS that was bad, had lots of water in it and oil stuff. Pretty #$%*ty stuff. IT runs great now. Smokes a little bit at first start up but goes awa within 20 seconds. Gonna ride it to work on tuesday. Can't wait.

Cevan · « **Reply #36 on:** October 17, 2011, 09:53:08 AM »

Damn that's looking good. I need a 1450 sq. ft. shop.

Did you have the chrome removed before painting the front fender?

TommyT · « **Reply #37 on:** October 17, 2011, 10:02:36 AM »

No i didn't. I just sanded it all with 40 grit then up to 200, coat of etching primer, then 2 coats of sandable primer. Skuffed with 400 grit and sprayed semi-gloss black. Not the best job but looks better than the rusty chrome. I'm planning on bobbing it someday but just want to get out and ride now before the rain comes.

nghisus · « **Reply #38 on:** October 17, 2011, 02:23:31 PM »

Quote from: Cevan on October 17, 2011, 09:53:08 AM

Damn that's looking good. I need a 1450 sq. ft. shop.

Check out the Yamaha XT 500 this guy built in his cramped little apartment. You can google it pretty easily

I'm not thread jacking. That's a great build man! And super duper fast too! I guess you were more worried about build than documenting but I love seeing all the little steps more than anything. ON your next build I'd love to see more details.

Anyway, keep up the good work!

seanbarney41 · « **Reply #39 on:** October 18, 2011, 08:02:59 PM »

Quote from: TommyT on October 11, 2011, 09:34:32 PM

OK got it all assembled and it is only running on 2 cylinders until you ev to about 3000 rpm then the 2 and 4 pipes get hot and revs right up. Pulled points cover off and points on 2-4 barely open compared to other side. Gonna attempt to adjust those and check timing before syncing the carbs.

hey TommyT...really don't mean to be a know it all...but...one set of points and ignition coil fires cylinders 1 and 4, the other set of points and ignition coil fire cylinders 2 and 3...nice lookin' bike by the way

lucky · « **Reply #40 on:** October 18, 2011, 09:17:23 PM »

Quote from: TommyT on September 25, 2011, 09:41:36 PM

With the carbs off and on the bench when I hook up the fuel it's leaking on the #2 carb between the body and the bowl. I cleaned off all the silicone #$%* the PO had put on there and cleaned it all out but still leaking a bit. Floats/needle and seats all look good. Float levels are spot on and everything was running great when tore down. Just sitting for the last 3 months without fuel i think the carb gasket dried out a bit letting it leak out.

Since it is a 1978 and those carbs had the accelerator pump on the number 2 carb make sure when the float bowl is off that there is supposed to be a little tiny 1/4 inch diameter "O" ring between the float bowl and the carb. The O" ring is is right over the check valve on the top edge of the float bowl.

Also make sure that when the float bowls are full of gas that when you open the throttle (engine not running) that you see all 4 of the nozzles squirt fuel into the engine. If they do not the check valve in the bottom of the accelerator pump could be at fault. and if the nozzles do spray fuel that ALL 4 of them work.

CLICK ON PHOTOS TO ENLARGE

lucky · « **Reply #41 on:** October 18, 2011, 09:26:12 PM »

Quote from: TommyT on October 13, 2011, 02:50:55 PM

Rode it around my shop complex a couple laps last night. feels great to finally get it riding. Still not running great, hope new points fixes that. The 1-3 points gap was almost .020 and the 2-4 gap was less than .006 my thinnest gauge. Adjusted those to .012 and it runs a lot better, but I believe timing is off as it's harder to start now. Not gonna mess with it until I get the new points in and adjusted. Also the #4 cylinder exhaust is warm but not nearly as hot as the others, has spark and fuel, any ideas there?

Could be those fuel nozzles. One may be blocked.

lucky · « **Reply #42 on:** October 18, 2011, 09:31:39 PM »

Quote from: TommyT on October 11, 2011, 10:07:18 PM

I'm gonna check it out with the dwell meter as well. I'm probably just going to order new points and condenser as well. Are the 77-78's different than earlier ones as well? Any advantage of ordering a complete points set with backing plate and everything or new points and condenser ok.

No advantage really. Just more convenient. When you put in the points PLATE just center it in the middle of the slotted holes.
Then adjust each set of points. Just a little detailed is all.

lucky · « **Reply #43 on:** October 18, 2011, 09:39:38 PM »

Quote from: TommyT on October 13, 2011, 02:50:55 PM

Rode it around my shop complex a couple laps last night. feels great to finally get it riding. Still not running great, hope new points fixes that. The 1-3 points gap was almost .020 and the 2-4 gap was less than .006 my thinnest gauge. Adjusted those to .012 and it runs a lot better, but I believe timing is off as it's harder to start now. Not gonna mess with it until I get the new points in and adjusted. Also the #4 cylinder exhaust is warm but not nearly as hot as the others, has spark and fuel, any ideas there?

Get the gap adjusted FIRST on each set of points.
Then adjust the plate clockwise or counterclockwise to get it to the where the the timing is right.

KEY OFF.

Get the plate in about the right place and then turn the engine with a wrench until the points start to open and have a multimeter (analog with meter and dial) hooked on each set of points one at a time and use the ohms X 1000 scale. When it fires you will see the meter jump. Do 1-4 then 2-3
It is better than a test light because a test light requires a certain amount of resistance to make the light work and then the timing is late. Also with a test light
the key has to be on to supply 12 volts and then the points can get burned.

lucky · « **Reply #44 on:** October 18, 2011, 09:41:58 PM »

One more thing..Can you tell us what you thought about those rear shocks?

Too soft,just right etc.,.

TommyT · « **Reply #45 on:** October 20, 2011, 04:32:39 PM »

OK that's a lot of info and good stuff there. I think most of the issues got figured out with plugged #4 carb and new points/condenser.

I'm gonna check the accel pump nozzles again. When I test it on the bench all with squirting fine.

TommyT · « **Reply #46 on:** October 31, 2011, 01:12:57 PM »

OK tore into the accelerator pump area this weekend. No fuel coming out of the nozzels at all. Can't even get spray to come out of them. Also the little diaphragm has 2 ears on it. Only the "out" nozzle has a hole in it. the "IN" side has no hole and the little bowl isn't getting any gas in there. Poked a hole in that with a small punch and now it fills but still doesn't spray. BUT the good news is it doesn't come back into the bowl so I know atleast one of the check balls is working correctly.

Now to clean the nozzles and passage ways. What do you guys think would be the best way to do so without tearing the carbs apart 100% again?

NP3 · « **Reply #47 on:** November 01, 2011, 04:38:14 PM »

Hey Tommy, nice build. Did I read correctly that you painted the frame with VHT rattle can paint? How about the tank and seat pan, rattle can also? If so, that is amazing! And I'd be curious to know how the paint holds up to daily wear and tear.

TommyT · « **Reply #48 on:** November 02, 2011, 11:45:14 AM »

The frame and gold on the tank are all spray paint but the black and clear are 2 stage from my spray gun.

lucky · « **Reply #49 on:** November 02, 2011, 03:37:22 PM »

Quote from: TommyT on October 31, 2011, 01:12:57 PM

OK tore into the accelerator pump area this weekend. No fuel coming out of the nozzels at all. Can't even get spray to come out of them. Also the little diaphragm has 2 ears on it. Only the "out" nozzle has a hole in it. the "IN" side has no hole and the little bowl isn't getting any gas in there. Poked a hole in that with a small punch and now it fills but still doesn't spray. BUT the good news is it doesn't come back into the bowl so I know atleast one of the check balls is working correctly.

Now to clean the nozzles and passage ways. What do you guys think would be the best way to do so without tearing the carbs apart 100% again?

Just remove the little rubber tube between the carbs that flow to the spray nozzles and spray some carb cleaner through till you see it spray out the nozzle. Protect your eyes!!!

The top edge of the float bowl as a little hole with a brass square thing in the hole.
That is where the "O ring goes. under that brass thing is the spring and check ball.
That keeps the gas from draining back down into the float bowl.

Now in the very bottom piece is another little square brass piece with spring and check ball.'This is the critical one. If it does not work right your motorcycle will NEVER run right. A new bottom plate with check ball is $85.00 and IS available. After I tried to clean mine 3 times with no success I bought a new one and now it works perfect.
I think what happened is the check ball gets corrosion and leaks or does not seal.

I have a spare diaphram and bottom plate but the check ball is no good. If you want it and try to find a new check ball the right size I can give it to you. My ADVICE, bite the bullet and buy a new one before they are no longer available.

BTW I am rebuilding a 1978 that has a gold frame with black tank too!!!

I sure wish you would tell me about those shocks.

News:

Author Topic: First Motorcylce 1978 CB750K. Cafe Build (Read 17897 times)

mrjack55