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Author Topic: CB350 Four scrambler projet + brat?  (Read 790 times)

Offline tahitianrider

  • Posts: 87
    • tomracingdesigns.com
CB350 Four scrambler projet + brat?
« on: Mar 05, 2019, 09:03:42 »
So few months ago I picked up a 73 CB350F that had been sitting for about 30 years, along with a second engine with carbs and a second frame.
They have not been stored in great location during all those year it seemed... lot of humidity and corrosion about everywhere.

My main project was to build the first CB350F as a 2 seater scrambler, and later on maybe sell the extra engine & frame, but I now had another idea, since I have tons of leftovers parts (tanks, shocks, etc.) from other projects to build a second bike with those parts.

I managed to restart the bike by rebuilding the carbs & ignition, and then completly rebuild the rest of the bike: re laced wheels with new rims, tires, changed the fork seals, made a handmade scrambler seat, treated the gas tank, etc. so it's starting to look cool IMO.
Only things lefts to do are "finish up" work like installing turns signals, new drive chain, pods (carbs already re-jetted) and final tune (carb sync, etc.)

For the second engine however I'm not quite sure if it seized or not... It sat for a long period without spark plugs, nor carbs & exhaust... I tried gently turning the crankshat nut behind the points cover but it didn't move and the bolt quickly broke inside, luckily I was able to remove it entirely so I just have to install a new bolt. I then spray some fogging oil in the cylinders, left it for a day. Then I tried to connect 12v power directly on the starter and it did crank a bit and I could feel (wind) from the spark plug hole so I guess the piston did move in the cylinder. I sprayed a lot more fogging oil then left it as is, haven't tried anything else yet since my priority is to finish the Scrambler build first.
But if I can get this engine to run again too I think a brat build would be cool, or maybe a cafe racer but I'd like those bike to be 2 seaters.
« Last Edit: Mar 05, 2019, 09:56:22 by tahitianrider »
'94 BMW K75 Racer
'84 Yamaha XJ 600 "Rocket" Racer
'76 CB 360 old school cafe
'96 CM 125 Brat bike
'80 CX 500 Racer
'73 CB350F Scrambler
www.tomracingdesigns.com

Offline pidjones

  • Posts: 738
Re: CB350 Four scrambler projet + brat?
« Reply #1 on: Mar 05, 2019, 10:05:36 »
If anything like the dohc 750s, you turned the wrong bolt. On these, you turn the bolt on the alternator rotor. Either way, you should remove the valve cover and put assembly lube (or at least motor oil) on the cam lobes. Personally, I'd fill the cylinders with oil and let it set for a week, then bar it over gently ~1/2 stroke, refill cylinders and let it set another week. Then bar it over to get most of the oil out followed by starter motor to get the rest down to just a coating. Did this with a '79 CB750F that had set in the open since 1999 with good success.
"Love 'em all.... Let God sort 'em out!"

Offline tahitianrider

  • Posts: 87
    • tomracingdesigns.com
Re: CB350 Four scrambler projet + brat?
« Reply #2 on: Mar 05, 2019, 11:07:46 »
It was the correct bolt because I have the service manual and it is bolt used to rotate the engine when setting the ignition timing, it is the bolt I use when I set ignition timing on my working 350F engine.
Thanks for the tip on removing the valve cover, I hadn't think of it and I have extra engine oil laying around, that's what I'm going to do!
As for the oil in the cylinder, I actually put fogging oil (similar to marvel mystery oil) since I heard it could help a lot free'ing up pistons, but maybe I'll try the engine oil in cylinders too.
'94 BMW K75 Racer
'84 Yamaha XJ 600 "Rocket" Racer
'76 CB 360 old school cafe
'96 CM 125 Brat bike
'80 CX 500 Racer
'73 CB350F Scrambler
www.tomracingdesigns.com

Offline WhyNot

  • Posts: 1245
  • ~~~If it ain't raining, I'm riding~~{iii}?~~prost~
Re: CB350 Four scrambler projet + brat?
« Reply #3 on: Mar 05, 2019, 13:14:42 »
So the blue bike now is the red bike, looks great.
2015 Toyota Taco DD now
2006 Harley Davidson Heritage Softail
1975 Honda CB750K5 needs carb work
1974 Honda CB350F2 needs tins painted (being lazy)
1972 Honda CB175K2 roller no engine
1972 Honda CB/CL350 Engines need roller
1972 Honda SL350K2 Frame for above engine
1972 Honda CB100K2 needs kicker shaft
1990 Mitsubishi MM runs, but no power
1984 Dodge D50 Beater was DD since 1997

Offline tahitianrider

  • Posts: 87
    • tomracingdesigns.com
Re: CB350 Four scrambler projet + brat?
« Reply #4 on: Mar 05, 2019, 13:38:30 »
So the blue bike now is the red bike, looks great.

Exactly! blue wasn't the original color anyway, it was olive green at first, I noticed when scratching paint. Thanks :)

The second bike is just an engine and a frame a the moment, but I already found a complete rear wheel, and a complete front end off a CB250G (similar to the CB360 but only use by the army in France at the time) I'm waiting to receive
'94 BMW K75 Racer
'84 Yamaha XJ 600 "Rocket" Racer
'76 CB 360 old school cafe
'96 CM 125 Brat bike
'80 CX 500 Racer
'73 CB350F Scrambler
www.tomracingdesigns.com

Offline tahitianrider

  • Posts: 87
    • tomracingdesigns.com
Re: CB350 Four scrambler projet + brat?
« Reply #5 on: Mar 13, 2019, 12:30:06 »
First 350 Four is now finished, I am just still waiting to receive its registration to test ride it which is pretty frustrating lol

And still gathering parts for the second 350 Four project, also waiting on oil sitting in the cylinders of the second engine to maybe unseize it, I might try to pour in petrol with 2 stroke oil mix inside the cylinders too.

'94 BMW K75 Racer
'84 Yamaha XJ 600 "Rocket" Racer
'76 CB 360 old school cafe
'96 CM 125 Brat bike
'80 CX 500 Racer
'73 CB350F Scrambler
www.tomracingdesigns.com

Offline WhyNot

  • Posts: 1245
  • ~~~If it ain't raining, I'm riding~~{iii}?~~prost~
Re: CB350 Four scrambler projet + brat?
« Reply #6 on: Mar 13, 2019, 12:35:41 »
Man, that looks nice. Wish I could get mine even going......darn carbs.

Did you have to change the carb. jets with that exhaust set-up?

Never mind, see you have pods on there.......
2015 Toyota Taco DD now
2006 Harley Davidson Heritage Softail
1975 Honda CB750K5 needs carb work
1974 Honda CB350F2 needs tins painted (being lazy)
1972 Honda CB175K2 roller no engine
1972 Honda CB/CL350 Engines need roller
1972 Honda SL350K2 Frame for above engine
1972 Honda CB100K2 needs kicker shaft
1990 Mitsubishi MM runs, but no power
1984 Dodge D50 Beater was DD since 1997

Offline tahitianrider

  • Posts: 87
    • tomracingdesigns.com
Re: CB350 Four scrambler projet + brat?
« Reply #7 on: Mar 13, 2019, 12:39:24 »
Thanks! I still have to fix one small leak on one of the carb that is still leaking a bit via the overflow tube, I'll try to swap the other bowl with one I soldered.

What's wrong with your carbs?

Yeah I did changed the jets with the pods & exhaust, if I remember correctly, I put 38 slow jet and 80 main jet. I also sync the carbs. I will adjust the fuel mixture screw when I'll be able to test ride it on the roads.
'94 BMW K75 Racer
'84 Yamaha XJ 600 "Rocket" Racer
'76 CB 360 old school cafe
'96 CM 125 Brat bike
'80 CX 500 Racer
'73 CB350F Scrambler
www.tomracingdesigns.com

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Re: CB350 Four scrambler projet + brat?
« Reply #8 on: Mar 13, 2019, 13:02:18 »
And still gathering parts for the second 350 Four project, also waiting on oil sitting in the cylinders of the second engine to maybe unseize it, I might try to pour in petrol with 2 stroke oil mix inside the cylinders too.

Try mixing ATF (transmission fluid) and acetone 50/50 and putting that in your cylinders. Its the only thing I've found that will actually penetrate past rusted rings on a seized piston.

Offline tahitianrider

  • Posts: 87
    • tomracingdesigns.com
Re: CB350 Four scrambler projet + brat?
« Reply #9 on: Mar 13, 2019, 13:20:15 »
Try mixing ATF (transmission fluid) and acetone 50/50 and putting that in your cylinders. Its the only thing I've found that will actually penetrate past rusted rings on a seized piston.

You mean something like that? because I just happen to have some


Nevermind I just found out that ATF means Automatic transmission fluid, I'll just get some on amazon then along with some acetone! thanks!
« Last Edit: Mar 13, 2019, 13:28:18 by tahitianrider »
'94 BMW K75 Racer
'84 Yamaha XJ 600 "Rocket" Racer
'76 CB 360 old school cafe
'96 CM 125 Brat bike
'80 CX 500 Racer
'73 CB350F Scrambler
www.tomracingdesigns.com