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Author Topic: Just bought a 1971 CB350 with 1500 miles. What to do with the motor?  (Read 1048 times)

Offline Wyld Bill

  • Posts: 101
So as much as I love to fabricate and I love the old cafe style bikes I'm going to build a 100% OEM or at least mostly OEM looking bike. So I started with HondaTwins forum but seems pretty dead over there.
Motor questions-
Should I try to run the engine as is or tear it down and inspect inside, clean out old oil, replace seals & gaskets etc. Should replace the piston rings? Should I port the head or just leave it alone? (this isnt going to be a cafe bike)
Since I havent started on this project yet and its going ot sit for another week or two, should I drain the old nasty oil and dump in some degreasing solvent or gas or kerosene in the engine crankcase to loosen up the old oil crud?
Where can I get my engine bolts zinc plated or get new bolts that are triple zinc plated or something?
What paint should I use to paint the engine case? HIgh temp? What color for stock Honda?
Is there any sort of coating on the engine head or is it just raw aluminum?
If I polish any aluminum engine parts how do I keep them from dulling or oxidizing? Do you clear coat them?

Thanks

Offline session101

  • Posts: 203
dude 1500 miles, run that shit!

do a compression check, and get it all running, if its pretty decent, might as well enjoy it while you can.

Offline alec.korver

  • Posts: 211
First and foremost, do a compression test. Then report back.

Offline noexit

  • Posts: 293
You're very likely to need new top end gaskets soon after getting it running, so you can do it now, or do it later. If you want to ride it first, it won't hurt things.

Offline Wyld Bill

  • Posts: 101
Its Winter in Maine so no need to ride right away.
Also I forgot to mention the kicker doesn't work so Ill need to pull the side case to see whats up with that anyways.
So if I'm pulling the heads to do the gaskets should I change the rings too since they are so old?
Also if I pull the motor it would be a good chance to clean it up and paint the base.

Offline TheCoffeeGuy

  • Posts: 386
    • The Coffee Guy's Blog
I would definitely pull the whole top end off.  Typical on these bikes is the cam tensioner rubber disintegrating with lack of use, they get dried out and just fall apart.  Rings should be replaced as well.  you might find when you pull the heads that there is corrosion or oxidation above where the pistons ere stopped the longest.  As well for the cost a carb kit should be installed.  For the cos i would also take it to a carb specialist and have then carbs cleaned ultrasonically.   Its really the only way to get all the small ports fully cleaned and smooth.  Finally the rubber should be addressed.  Old tires cn look good but just fall apart  at 50mph all of a sudden.
www.thecoffeeguy.ca Not your ordinary Blog site.

1968 Harley Aermacchi ML 125 Rapido, restored
1972 Honda Cl 450 engine rebuild, a day rider soon
1980 Suzuki GS850GL Street Brat  My other day bike
2000 Harley 1200 Sport S My day bike

Offline Wyld Bill

  • Posts: 101
Thanks Thecoffeguy. Do you think I should put anything in the lower unit for now to loosen up any old oil sludge?
Yeah my buddy wants me to just try to start it but I am also worried about crud or corrosion in the cylendars in particular up above the pistons.

How much is a carb rebuild kit and cam chain rubber and where should I buy them?
How about rings? Shouls I buy new old stock OEM or new non OEM ??

Offline TheCoffeeGuy

  • Posts: 386
    • The Coffee Guy's Blog
Bill
If you are going to drain the lower end later anyhow, you may slip a half liter of varsol in and slosh it around.  I would first drain any liquid oil that comes out, then put the solvent in.  once you have sloshed the solvent around a bit each day for a week or so, then drain it.  Drain it for a long time.  After a month or so of draining, put say half a quart of thin oil in and slosh that around, say a full 5 weight oil.  That will thin out the solvent that might have remained in any of the smaller recesses, then drain that.

i buy carb kits from, http://www.siriusconinc.com/   they have reasonable priced ones and I have never had an issue with any products form them.  They also have a lot of other cables and rubbers and seal etc.

The Cam part will probably only get from a dealer.  Your local guy is a good resource.  if you can find an old guy there he can give you a lot of help.   All the Rings and stuff should either be new OEM or new old stock.    Even after market if you find thema re fine.  online i always search with the actual part number.  this can usually be found on fiche at cmsl.com
www.thecoffeeguy.ca Not your ordinary Blog site.

1968 Harley Aermacchi ML 125 Rapido, restored
1972 Honda Cl 450 engine rebuild, a day rider soon
1980 Suzuki GS850GL Street Brat  My other day bike
2000 Harley 1200 Sport S My day bike

Offline surffly

  • Posts: 2872
Miles mean almost nothing at all.
The years have done more damage then anything.  Honestly a bike that has been used and maintained that has a million miles might be better off then something sitting for 40 years doing nothing.

Blindly tearing it down is kinda stupid as well.  Just spending money and doing work for the sake of work with no real light at the end of the tube.

Can't really tell anything untill you get the motor running and warmed up.
Motor needs to be hot for a compression test.

You have all the micrometers and other related engine rebuilding tools needed?

Offline surffly

  • Posts: 2872
I only buy OEM Honda parts for the motor.
You can get 99% of things right at the dealer or dealers online
The aftermarket stuff like carb parts are generally wrong and poor quality.  Also they are the same if not more money then the correct honda part.

You do have a factory manual right?

Offline 1slowkayzee

  • Posts: 12
Honestly, I would have to agree with surffly. Don't cause yourself headache for no reason, spend your time on other areas of the bike first especially if it already runs without issue. Drive it till it breaks

Offline Wyld Bill

  • Posts: 101
Ok an update. It is pretty much siezed. I have a gasket kit on the way. I'll order some rings and the cam chain friction plate thing. I just pulled the carbs off and cleaned them last night. Not too bad I must say I've seen a lot worse. One problem though is the floats are destroyed. Anyone know if the floats from my 1981 CM400 carbs would work? It looks like they would be a nice upgrade,..that and the float needle valve. So will I need any special tools besides a valve spring compressor and a cylendar hone to pull the head off and go through that with new gaskets and seals? As far as the base I think I'll just flush it out, maybe pull the side case off and pull the clutch pack apart and clean or soak the friction plates, then put that back together.
Anything I need for parts besides a standard engine gasket kit, two piston ring sets, and new cam chain tensioner, and some new SS bolts and nuts?

Offline Wyld Bill

  • Posts: 101
Bill
If you are going to drain the lower end later anyhow, you may slip a half liter of varsol in and slosh it around.  I would first drain any liquid oil that comes out, then put the solvent in.  once you have sloshed the solvent around a bit each day for a week or so, then drain it.  Drain it for a long time.  After a month or so of draining, put say half a quart of thin oil in and slosh that around, say a full 5 weight oil.  That will thin out the solvent that might have remained in any of the smaller recesses, then drain that.

i buy carb kits from, http://www.siriusconinc.com/   they have reasonable priced ones and I have never had an issue with any products form them.  They also have a lot of other cables and rubbers and seal etc.

The Cam part will probably only get from a dealer.  Your local guy is a good resource.  if you can find an old guy there he can give you a lot of help.   All the Rings and stuff should either be new OEM or new old stock.    Even after market if you find thema re fine.  online i always search with the actual part number.  this can usually be found on fiche at cmsl.com

Whats Varsol?? I was thinking someone would tell me some weird concoction that I dont have. I have gas, diesel, kerosense, degreasing solvent....none of those would work?
So,...if I buy an new, old stock cam tensioner would that be junk too??

Offline surffly

  • Posts: 2872
Why are you ordering any parts without knowing whats wrong?
Maybe the motor just needs rings, maybe it needs to be bored out.  You will have no idea till you measure everything.
There is no magic list of things you need.

Offline noexit

  • Posts: 293
Get the kick starter fixed and some good carbs and fire it up. You probably don't need rings. You don't need a bore. It will be fine.