Author Topic: -Tourette- 1978 CB750F (Read 3850 times)

LokisTyro · « **on:** May 30, 2015, 11:57:00 AM »

Well. Here's my first bike. A 1978 neglected and dropped F. Ran and drove despite the valves being yards out of adjustment and running very rich. Tappets were pretty loud on one side, hoping to not have to did into the head right away (not sure where the early vavletrain failure is on these), I'll find out when it's refired. Ordered a bunch of parts for it. Clutch cable, tach cable seal, 3 brake caliper pistons and seals, a bleeder screw that was previously broken off.. contact plate gasket, petcock, brake pads, a carb rebuild kit for 1 carb, air screw o-rings, plug caps and a Clymer. Napa had an oil filter and plugs so I stocked up. Haven't done too much yet aside from replaced a bowl and bowl drain plug gasket and pull the sticky brake calipers off and cleaning out the masters checking/cleaning the pinhole with an E string, .038 or something like that. I'll be repainting the calipers since they're being rebuilt. The tank and tail section were repainted by POs.. the tail painted black with a brush, which is from another bike that the guy put on for me. The tail section was cracked on the original and I didn't care for the shaved seat. Pics show both. I haven't had much luck finding a tuning guide for the PD42A carbs so that's my only real issue right now. I want to "reset" the carbs before I fire it again. It didn't want to idle without the choke on before, but there was a missing clamp, and loose ones and fuel leaking from one bowl and some other spots and everything thinkable is probably out of adjustment. I'm actually surprised it ran as strong as it did, so, I bought it... The plan is to get it ready for this season and then tear it down for a mostly stock restoration with a bit of weight reduction and clean-up of the overall look I guess that's all for now.

LokisTyro · « **Reply #1 on:** May 30, 2015, 07:29:41 PM »

Adjusted the valves to .002 on the intake side and .004 on the exhaust side. My fears have gone the way of the rotary phone. She's so quiet now and will actually idle down to 1250. Not bad for not knowing what the carb settings should be at and having a visible exhaust leak on number 4. Next is an oil change with risoline and waiting for parts while I clean things up and check the timing and do all the routine maintenance.

LokisTyro · « **Reply #2 on:** June 14, 2015, 12:08:24 PM »

So, I decided to pull a few things off because I need to paint the battery/electronics box and replace some rubber hoses and lines while ditching the stock crankcase breather and figure out where a couple other vent? tubes are suppose to go that were up by the battery. All the electrics work on the bike, which is surprising after what I found. I know jack about electric bits and bobs! So my question is this, would the corrosion in the harness plugs cause itself to bridge connection and melt? Also, if I have both shocks disconnected and give it a wiggle, is that a sufficient way to check the swingarm bushings?
On the bright side I can now see the sprocket and chain after cleaning it for an hour or so.. And after removing the rear signals, chain guard and rear "bumper" the look gave me some needed motivation. Now I'm contemplating treating it all down and doing a quick refresh...
Carbs are coming off again to do a proper cleaning and repacking. Dropping the oil pan too see what's what. Might have to pull the engine if the primary is loose. Seems a bit noisy.. First oil change turned black instantly. Risoline must do a great job of loosening crud up.

madmtnmotors · « **Reply #3 on:** June 14, 2015, 12:36:35 PM »

That particular connector is where the "sub harness" from the alternator connects to the main harness. This is probably the highest amp connector on the whole bike and the additional resistance from the corrosion I see probably took it "over the top". The sub harness can be replaced, as well as the connector on the main harness. I have had to replace more than one of these.

http://forums.sohc4.net/index.php/topic,137351.msg1549191.html#msg1549191

LokisTyro · « **Reply #4 on:** June 14, 2015, 01:27:17 PM »

Thanks, mad mountain. Great job on the ones shown in the thread you linked for me. Looks better than new! I'll order some block and clean up all the pins in the meantime since I have that tool on hand(dammit) and I haven't found any bare wire that could explain it. It needs to be done anyway. Good times here I come!

70CB750 · « **Reply #5 on:** June 14, 2015, 03:05:33 PM »

Do you know how many miles on her? They tend tóeat valve guides between 25-30000 miles. To prolong the life, use 20W50 oil in her - like Valvoline motorcycle oil.

LokisTyro · « **Reply #6 on:** June 14, 2015, 08:06:17 PM »

Almost 24,000 miles. I was hoping to get through the summer by taking it easy on her, saving some money and dig in during the winter but we'll see. I might be too impatient. I want to rebuild my first bike!

seanbarney41 · « **Reply #7 on:** June 14, 2015, 08:26:35 PM »

Hi there...nice bike. I think the F2/3 is the best riding version of the SOHC4. Don't be in too much of a hurry to rebuild your engine. I have an F3 with 30,000 on it and it still goes fine...and it was not a well cared for bike either.

I am curious what you did with that shaved down seat. I like it and would possibly purchase it from you.

LokisTyro · « **Reply #8 on:** June 16, 2015, 02:22:14 PM »

The seat you're interested in belongs to the previous owner. I opted to take another seat with better plastic when I purchased the bike. If you'd like I can contact him and see if he'd like to sell it or if he'd be willing to talk to you directly.

seanbarney41 · « **Reply #9 on:** June 16, 2015, 02:55:11 PM »

Quote from: LokisTyro on June 16, 2015, 02:22:14 PM

The seat you're interested in belongs to the previous owner. I opted to take another seat with better plastic when I purchased the bike. If you'd like I can contact him and see if he'd like to sell it or if he'd be willing to talk to you directly.

probably more trouble than it's worth...I would only pay maybe $50 for it depending on some better pics

LokisTyro · « **Reply #10 on:** June 17, 2015, 08:47:20 AM »

From what I know it was a shaved stock seat recovered. It wasn't very comfortable when I test rode the bike with it on. If you have a seat with good foam it should be easy enough to make something a little nicer with a cover of your choice.

LokisTyro · « **Reply #11 on:** May 30, 2017, 03:36:52 PM »

I've taken the MSF Basic Rider Course over the weekend with a buddy for his B-Day. We both aced the test

Not very difficult but we're proud all the same. Went to the DMV a few minutes ago and now I'm officially licensed to ride

I'm looking for a CB125 as a DD if anyone has one in WI or very near to it.

LokisTyro · « **Reply #12 on:** May 30, 2017, 03:38:36 PM »

Looking for a 750F frame and Jugs as well, forgot to mention that.

LokisTyro · « **Reply #13 on:** June 27, 2017, 04:07:06 PM »

Been working my butt off on this thing. I'll get some pics up soon to make it a little interesting for folks. I got the carbs completely disassembled and ultrasonically cleaned. Hooray for harbor freight. Thing works pretty damn good and the heater is super quick even when filled to the max.

So now I'm waiting on an accelerator pump diaphragm (thought it was okay until I looked at the other side! nasty!) and the last carb kit. I was sent a different brand even though I ordered from the same place. I've also got some samples of F-5 SAE wool coming so I can make my own gaskets/vacuum seals? What are those things called? Has anyone had any issues replacing the rubber sides with o-rings or is there a square alternative I should use instead? I don't PLAN on rebuilding or tearing the carbs apart again so I want to do things right the first time, as well as I can anyway. Does anyone have dimensions of the woolies that I need to make? the old ones all ripped and I don't have any way to measure the ID of that location. I can get the "ridge" measurement but not inside of that. That would be a great help so I don't make these things undersized. I wont have much material to play around with. I ordered a sample in 1/8" thickness, will that be enough?

I'll have to get a pic but I have a hard time following wiring diagrams without pulling my hair out. My old phone with my reference pictures took a poo. I have numbers labeled so that'll help get the pins in the correct spot where the rectifier and some other wires melted the plastic connector. Kind of a heads up I guess $:-\$

I took the exhaust off to get the bike on a swingarm stand and found that there weren't any copper or alu gaskets inside. Kinda #$%*ty but I hope the bike will run better once it has them. I have almost everything I need onhand except for handlebars, an oversize bleeder for one of the calipers and maybe some new turn signals and taillight. Definitely need some new tires too. This will be the first big bike that I'll be riding for extended periods so I'm looking for something all weather with good longevity. Any recommendations? I don't want to spend a massive amount on them but I wont cheap out on them either.

Drag bars were installed on the bike and I liked the forwardish riding position but I have stock lower control positions. I've only ridden the bike a total of maybe 15 miles. I'm 5' 10" and it seemed okay for a short period. Anyone think I'll be uncomfortable on 100 mile rides? Once I get it this thing going it'll just be a beater and a DD on my 10 mile trek to work. I really don't want to spring for rearsets..

madmtnmotors · « **Reply #14 on:** June 27, 2017, 07:03:02 PM »

Quote from: LokisTyro on June 27, 2017, 04:07:06 PM

the last carb kit. I was sent a different brand even though I ordered from the same place.

Aftermarket carb kits should have Viton rubber parts. Non-Viton aftermarket fuel system rubber will fail quickly when exposed to ethanol laced fuel. My carbs started leaking and the rubber parts were turning to goo after just one week of exposure to ethanol laced fuel. Original Honda parts work well too.

Quote from: LokisTyro on June 27, 2017, 04:07:06 PM

I took the exhaust off to get the bike on a swingarm stand and found that there weren't any copper or alu gaskets inside. Kinda #$%*ty but I hope the bike will run better once it has them.

Clean the exhaust port in the head really well. The old gaskets tend to blend into the port once they are generously coated with carbon. The old ones usually have to be pried out and often there will be more than one since the last guy didn't recognize the presence of the previous crush gasket.

LokisTyro · « **Reply #15 on:** June 28, 2017, 02:10:21 PM »

That's a great tip. Saves me from being that guy. I assumed they were not installed because of the carbon buildup on the exterior of the head around the ports but maybe they were reused.

LokisTyro · « **Reply #16 on:** June 29, 2017, 06:55:44 PM »

Sure as #$%*. With a light and some emery paper revealed some copper. Gaskets were so flat I thought they were machined lol
Made a little progress last night and today. Cleaned up the exhaust flanges and flowers and removed the clutch cable.
Do I need to find shorter brake hoses for drag bars? All the cables and hoses were stuffed in by the headlight, I don't think that's normal. I'd like to have the proper length since they need to be replaced in the front..

LokisTyro · « **Reply #17 on:** July 04, 2017, 06:45:02 PM »

Haven't finished Tourette so I thought why not. Runs strong, needs work.
1975

LokisTyro · « **Reply #18 on:** July 05, 2017, 10:15:34 PM »

About half finished with the carbs. Got the last carb kit and accelerator pump diaphragm so I threw that in. One carb left and I need to cut out the felt and figure out the best replacement for rubber rings on the shafts. And then to try and reassemble the whole mess and bench sync the rack. Figured I'd show a pic of the bike as she sits now. Not pretty but I'm learning and having fun.

Well it's almost fixed...

LokisTyro · « **Reply #19 on:** July 06, 2017, 04:12:35 PM »

Should I install the 110 jets for an UNI element (red one)? New 105's went in already, but I have 110's that came with the carb kits. The exhaust is pretty open, probably not much left of the packing. Seemed to be running well when I first got the bike but I never did any plug chops..

LokisTyro · « **Reply #20 on:** July 19, 2017, 03:33:14 PM »

Going to button the carbs up this weekend.

Any thoughts about leaving 105 jets in over the 110's I have on hand?

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Author Topic: -Tourette- 1978 CB750F (Read 3850 times)