Author Topic: '78 CB750K Project #1 - Cafe-like Racer-ish Bike (Read 37951 times)

Stoli · « **Reply #75 on:** June 05, 2013, 08:34:39 AM »

Quote from: Blitzburgh207 on May 28, 2013, 06:02:44 PM

That looks great man, good work! ps you'll love that muffler

Hey Blitz,

Where did you get your muffler and is there any muffling going on? Looks like Cone Engineering, Dime City and Cycle-X all sell what looks like the same thing but can't tell if there is some type of baffle inside or not.

Blitzburgh207 · « **Reply #76 on:** June 08, 2013, 09:30:10 PM »

Quote from: Stoli on June 05, 2013, 08:34:39 AM

Quote from: Blitzburgh207 on May 28, 2013, 06:02:44 PM
That looks great man, good work! ps you'll love that muffler

Hey Blitz,

Where did you get your muffler and is there any muffling going on? Looks like Cone Engineering, Dime City and Cycle-X all sell what looks like the same thing but can't tell if there is some type of baffle inside or not.

I bought mine from Cycle-X because that's who made my exhaust so I knew I wouldn't have fitment issues. It's slightly baffled but straight through. Pretty loud but has a nice tone to it. Prob not the best if you do a lot of group riding but I'm solo 90% of the time so it works for me. I also like that drivers around me in traffic know I'm there.

Stoli · « **Reply #77 on:** June 11, 2013, 03:27:07 PM »

Test drive & initial thoughts:

Much more comfortable than anticipated. I expected the clubmans to be rough on the lower back but that is not the case. I think the key is to get the rearset pegs in just the right place. That is a good reason why you should not buy rearsets that bolt on unless they also have a position adjustment, and I can't imagine such a thing exists for all leg lengths and torso heights. Adjust the handle bars where you like them, then sit on the bike and find the perfect location for the pegs, then make your own or have someone else fabricate mounting brackets. I was wondering if my brackets would not be solid enough but they are fine. I weigh about 200 and can stand (and bounce) on them with no deflection at all.

I was also surprised by the ease in which the bike maneuvers and turns. I suspect this is due to the lower center of gravity caused by the seat and handle bars.

Overall, I am extremely pleased at how the bike performs.

Stoli · « **Reply #78 on:** June 11, 2013, 03:30:33 PM »

Phase 1 - Initial Carb config and adjustment

Since I am new to this and this engine hadn't turned over in 20 years, I thought I would start out by getting as close to stock aspiration as I could. Unfortunately the exhaust was beyond repair so I started out with the stock airbox, an EMGO filter and a 4-1 Mac exhaust with a baffled muffler. To compensate for the 4-1, I put in 120 main jets and hoped for the best. No other modifications to the carbs at this time. Adjusted the valve clearance, idle screw, timing and did a carb sync all according to manual. All in all, not too bad. Seemed to run a little hot which was probably due to a lean mixture in the lower throttle ranges (no changes to the slow jets or needle height yet). It would also stall out at stop lights unless I kept a high idle (1200+).

Lesson Learned (Carb Cleaning) - The slow jets on the 77-78 PD42 carbs are pressed in and the shop manual has a note that says to not remove them. So I didn't. Well, the guys that wrote the manual were not anticipating the bike to sit for 20 years with fuel in it, so the correct thing to do is pull out those slow jets to clean them. I grabbed them with some pliers and gave them a very gentle twist until I heard a slight click (snap?) as the stem of the jet released. Then I pulled them straight out. Pretty easy procedure and only slight marring on the sides of the jets that won't affect performance.

Stoli · « **Reply #79 on:** June 11, 2013, 03:33:35 PM »

Phase 2 - Pods

After a few hundred miles, I changed the oil and filter and put on the pod filters. I got the APE pods which seemed to be similar in quality to the K&Ns but not so expensive. I also configured the carbs as follows:

Slow Jets - 42
Needle shims - 1mm (2 x M2.5 flat washers honed to .0195" each).
Main Jets - 135

Adjusted the idle screw, timing and did a carb sync all according to manual. Noticeable performance increase and no adverse side affects from the pod filters. Also resulted in a very pleasing and more throaty sound from the engine. Pleasantly surprised since I was expecting performance issues. After trying to get the engine to bog or act in an adverse manner, I found the only way to do this was to snap the throttle to full in the 50MPH range (3500 RPM in 5th). That resulted in a 2-3 second hesitation before a steady acceleration. It was, for the most part, something that I wouldn't normally do though and a smooth but quick advance (approx 1 second from 1/3 to full throttle) in the same regime resulted in a nice smooth acceleration with no bogging or hesitation. I expect that I am running a little rich at this point since my jet sizes are targeted at a less restrictive muffler. That will be Phase 3.

Also need to tweak the idle as I can't get it under 1100 at this point without stalling out.

Blitzburgh207 · « **Reply #80 on:** June 11, 2013, 07:06:43 PM »

Glad to hear you're getting good results right off the bat! I would imagine you should be able to get it to idle a little lower fine tuning the idle screws and timing/points gap. Are you using the points ignition? I threw a pamco on mine during the 836 rebuild and I'm able to get it to idle as low as 650-700rpm once warmed up, even with the stacks and cam - very happy with it.

Stoli · « **Reply #81 on:** June 12, 2013, 09:20:52 AM »

Hmmm. Hadn't considered the ignition. I'm using points. I've got a dwell/tach meter on order and will try to fine tune all that stuff over the weekend. If that doesn't do it I will recheck the float levels and then do a plug chop to see if I should switch to 40s on the slow jets. Heading up to Laconia later this week weather permitting.

Stoli · « **Reply #82 on:** June 13, 2013, 12:59:22 PM »

Phase 3 -

Put on the Cone Engineering "Shorty". Great sound. Took it for a quick spin but it started to rain so cut it short. I also mounted an old Honda Wing on the side cover.

edhaeuser · « **Reply #83 on:** June 18, 2013, 12:41:21 PM »

Very nice!

Stoli · « **Reply #84 on:** July 21, 2013, 05:09:27 PM »

Not much of an update. More like a check-in to keep my post alive. The bike has about 1500 miles on it since it's rebirth. I'm having too much fun to do any plug chops yet. It is running like a champ so part of me says why bother?

I played the idle screw adjustment game for a few days when I first got the bike back on the road but that got old real fast. Problem was that it needed full choke to start but would roll back very quickly and die. I found a sweet spot around 1/2 choke where the bike likes to warm up at. Full choke to start, then smoothly back to 1/2 and she's happy at about 1500-2000 rpm until warm. Once I figured that out, the idle screw hasn't needed adjusting in over 1000 miles.

I wish I got into this 20 years ago. Probably didn't have the time back then.

Stoli · « **Reply #85 on:** July 21, 2013, 05:34:49 PM »

My son and I have been going on a lot of rides together. He picked up a '77F last summer. The paint job was done by the PO (rattle can on a budget) but we have cleaned the carbs and made the necessary adjustments and other than a little shimmy at around 45 MPH, his bike is running great as well. Not sure if that is caused by steering stem bearings or an unbalanced wheel, or something else, but it seems to ride smooth on both sides of 45.

USCG_C130 · « **Reply #86 on:** July 21, 2013, 05:57:57 PM »

great job on the tank i ended up not doing dents because i was a bit intimidated of screwing something up but you have me wishing i would have, great build keep up the good work

Stoli · « **Reply #87 on:** July 21, 2013, 07:20:03 PM »

Thanks CG. I'm ex USAF myself. Have spent more than a few hours in a C-130.

I very briefly went through your build and it's impressive. Will be more thorough when I have some time. I anticipate needing to create my own wiring harness on my 3rd project so will undoubtedly take a few pointers from your experience. You must be chomping at the bit waiting to get your tank and seat back.

iron_worker · « **Reply #88 on:** July 21, 2013, 07:27:03 PM »

Great looking bike! Looks like you're having a blast riding too.

IW

Stoli · « **Reply #89 on:** July 21, 2013, 07:34:50 PM »

Quote from: iron_worker on July 21, 2013, 07:27:03 PM

Great looking bike! Looks like you're having a blast riding too.

IW

Thanks. Typically I like building things more than using them, but this bike has proven different. I did enjoy the build but riding it is a lot of fun. There are a lot of woodsy back roads in my area with hills and twisties which never seem to get old.

iron_worker · « **Reply #90 on:** July 22, 2013, 07:16:12 AM »

I'm jealous! I have to drive for hours just to find a couple twisties!

The closest thing to twisties I have here is on/off ramps. lol

IW

Bankerdanny · « **Reply #91 on:** July 22, 2013, 07:45:40 AM »

Quote from: Stoli on July 21, 2013, 05:34:49 PM

My son and I have been going on a lot of rides together. He picked up a '77F last summer. The paint job was done by the PO (rattle can on a budget) but we have cleaned the carbs and made the necessary adjustments and other than a little shimmy at around 45 MPH, his bike is running great as well. Not sure if that is caused by steering stem bearings or an unbalanced wheel, or something else, but it seems to ride smooth on both sides of 45.

Read this to diagnose the shimmy. I used Mike's advice to cure the head shake on my Goldwing, worked like magic. Lots of other great advice at his site too. http://www.motorcycleproject.com/motorcycle/text/shucking.html

lwahples · « **Reply #92 on:** July 22, 2013, 08:35:21 AM »

That bike is sharp! Like the seat.

65Ch3v3LL3 · « **Reply #93 on:** July 22, 2013, 08:45:13 AM »

Good looking bike.

onetruepunk87 · « **Reply #94 on:** July 22, 2013, 05:18:33 PM »

Bike turned out great! How do you like the cone muffler compared to the MAC can? It looks sweet, I was thinking about getting the MAC performance baffle on my '77 but i might go with that. Did you have to do anything to get it to fit on the header?

Stoli · « **Reply #95 on:** July 22, 2013, 07:18:51 PM »

There is a significant noise difference between the Mac and the ConeEng obviously, since the Mac has a baffle. I only used the Mac for a few days so can't give you a performance comparison. I do like the ConeEng and plan to keep it on this bike. If you don't like loud, then you might want to look into the baffled ConeEng. It is a bit longer but I still like the look.

The ConeEng can slipped right on the Mac header like a glove. Just make sure you order the right size for your header. I used the clamp that I got with the Mac to secure the ConeEng to the header and ordered a second clamp from ConeEng when I ordered the can and used it to support the unit. You can weld a bracket on to the can (like the Mac has) but I didn't want to go that route so I made a bracket to secure the unit on to the center stand bracket using the second clamp.. I'll take a pic if you are interested. It was intended to be temporary but works well and isn't too hideous so I will probably keep it that way. Might spray some paint on it over the winter.

onetruepunk87 · « **Reply #96 on:** July 22, 2013, 09:47:43 PM »

Thanks for all the info! If you get a chance to take a picture of the bracket you made up I'd love to see it. The MAC muffler is much more quiet than I expected. Riding with my brother the other day I couldn't even hear if my bike was running, so I'd definitely like something louder.

Stoli · « **Reply #97 on:** July 23, 2013, 07:42:57 AM »

Several web sites sell that Cone Engineering can but I think you will find the source to be the cheapest. Noise is relative I guess. It is still not as loud as most of the HDs around here.

Give me a day or so to get that pic. I'm on the road until Thursday.

RAFster122s · « **Reply #98 on:** July 23, 2013, 01:01:33 PM »

Nice work...have you considered your final paint scheme yet?
Liked your sled to extract the bike from the basement.
Work smarter, not harder...

Stoli · « **Reply #99 on:** July 23, 2013, 03:23:43 PM »

Quote from: RAFster122S on July 23, 2013, 01:01:33 PM

Nice work...have you considered your final paint scheme yet?
Liked your sled to extract the bike from the basement.
Work smarter, not harder...

It's amazing what you can move with simple machines - levers, fulcrums, pulleys ...

Everyone who has seen the bike in person has advised me to keep the matte black color and it has really grown on me so when I get around to putting the final coats on, I plan on matching the primer coat that is on there now.

I am about to start a similar bike (project #2) that will have a little "classier?" look, but I like the unrefined look of this bike.

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Author Topic: '78 CB750K Project #1 - Cafe-like Racer-ish Bike (Read 37951 times)