Author Topic: cb350 twin gurus! help needed! seized engine? (Read 13804 times)

mikedialect · « **on:** May 21, 2007, 10:12:13 PM »

Hello!

I have a 69 cb350 that I was happier than a pig in you know what with until today. I was visiting my old man in the VA hospital and two blocks after I left I heard a PING! and the bike suddenly died. I pulled off and did a quick visual inspection in the way that non mechanics do... I checked for the obvious stuff. No drips, no chain break- nothing. I've got gas, I've got oil, I've got battery power. Petcock is sweet as they come and gas is flowing alright. I try cranking it over a few times and she's cranking over. Starter is trying to do her job, gas is trying to burn, etc. A few tries into this I give up. I have no idea what is wrong, but the bike won't turn over at all now. Kick start won't roll over. It's stuck. Presumably seized.

Now- here are a few symptoms leading up.

The bike was running GREAT for about 6-700 miles.

Oil change about 2-300 miles ago- checked level each ride.

Back firing was occurring on start up recently. I'd let her warm up a bit and it would go away.

Today, when I was out and about earlier, the idle crept up to 3k and stayed there intermittently. The bike was getting a touch of hesisitation in the lower gears. Felt like it was missing.

Then, she died.

Now, like I said, I think it seized, but I'm no mechanic. I'm a tinkerer and I haven't had a ton of motorcycle experience. I'm curious about two things. 1) I wonder what the hell happened. 2)I've been looking for a parts bike for a while and I haven't been able to come across a 69 with any luck. I was wondering if it would be possible to put a different engine in the frame without any serious difficulty. Maybe a 71? I see tons of those around here.

Maybe that all sounds absolutely silly. I don't know much, but I do know that I want to keep this thing on the road. I loved how she rode and I don't mind working on her. I want to keep this classic alive and not parted out unless I have no other choice.

So, any and all thoughts are welcomed. I'm in Minnesota. I'm young, but I know how little I know, so I come to this board that has been so helpful in regards to my 750.

thanks!
(here is a picture for reference)

750goes · « **Reply #1 on:** May 22, 2007, 12:51:48 AM »

put it in gear and try and push it - does it move at all ?? backward or forward?

was the motor real hot when it "siezed"?

I'm not sure if you can put a different motor in - more help needed......

sorry to hear your problem - looks like a real nice bike.....

mikedialect · « **Reply #2 on:** May 22, 2007, 05:05:05 AM »

Quote from: 750goes on May 22, 2007, 12:51:48 AM

put it in gear and try and push it - does it move at all ?? backward or forward?

was the motor real hot when it "siezed"?

I'm not sure if you can put a different motor in - more help needed......

sorry to hear your problem - looks like a real nice bike.....

In gear it wont roll. I assume the bike the bike wasnt too hot as I had it parked for a while, but it was warm out, so my concept of its cool down might have been skewed.

ohiocaferacer · « **Reply #3 on:** May 22, 2007, 05:27:29 AM »

Sounds like your cam chain broke.......the twins are known for this.

Take your points and alternator covers off and see if you can rotate the cam, by turning the small bolt between the points plates. Be careful with this bolt....as it threads directly into the end of the cam. Also....try putting a 14mm wrench on the bolt in the middle of the alternator and try rotating it counter-clockwise.

If you have to rebuild the motor....dont just ditch that motor. Those early 350 twin motors are very hard to come by and if it was me....i'd rebuild it rather than put in another motor. That motor actually has a better cam profile and head to allow higher rpm's......and with that bike being so clean...keep the original motor.

Hope this helps,
Greg
www.OHIOCAFERACERS.com

bill440cars · « **Reply #4 on:** May 22, 2007, 07:04:08 AM »

Yeah, any 350 twin motor will work (CB/CL/SL) but, I'm with Greg on this. I wouldn't swap it out either. You may not be much of a mechanic but, with the help of a manual and the guys on this forum, you shouldn't have much trouble. There are several here who are quite familiar with the 350 twin and they could probably talk you through it(Greg of ohiocaferacer, seaweb, CBGBs and Raul for sure. And more, I'm sure, that I'm just not thinking about) I really hate to name names because I usually leave some out that could help, and I feel bad about that. Most folks are here for the reason I am, to learn, pick up ideas, share ideas and to help when and where we can.

BTW, that reallyIS a sharp looking CL350!

Later on, Bill

mikedialect · « **Reply #5 on:** May 22, 2007, 11:44:35 AM »

Quote from: ohiocaferacer on May 22, 2007, 05:27:29 AM

Sounds like your cam chain broke.......the twins are known for this.

Take your points and alternator covers off and see if you can rotate the cam, by turning the small bolt between the points plates. Be careful with this bolt....as it threads directly into the end of the cam. Also....try putting a 14mm wrench on the bolt in the middle of the alternator and try rotating it counter-clockwise.

If you have to rebuild the motor....dont just ditch that motor. Those early 350 twin motors are very hard to come by and if it was me....i'd rebuild it rather than put in another motor. That motor actually has a better cam profile and head to allow higher rpm's......and with that bike being so clean...keep the original motor.

Hope this helps,
Greg
www.OHIOCAFERACERS.com

I was thinking it might be that. I've never fixed something that 'mechanical' before, so I will definitely be looking for some guidance. I will take your advice and try those things. I actually am moving into a new apartment that has a garage with the goal of being able to do some work on my bikes. Unfortunately I'm in 4 summer classes this year, so I'm not sure I will have much time to take this apart and get it back together in time for any enjoyment this year. I was thinking an engine swap would be the best quick and dirty way to get her rolling again.

I guess I can see the purpose of trying to keep this as it is without an engine swap. I've never had a serious break down before, so I've got that pain for the first time and I'm feeling lost, you know? It's a shame, too because this bike has been my favorite. I've resisted selling it several times to folks who have offered to buy it.

SO, we know that it can be swapped, but in hopes to keep it original swapping wouldn't be a good idea? Any otehr advantages or disadvantages outside of the mentioned cam situation?

I've spoken to pdpimp about getting together, but I'm very interested in meeting any gurus in the area if there are any!

dusterdude · « **Reply #6 on:** May 22, 2007, 11:51:07 AM »

nothing wrong with changing engines,but as nice as your bike is,keep the stocker too in case you should decide to fix it in the future.

mikedialect · « **Reply #7 on:** May 22, 2007, 01:49:47 PM »

Quote from: ohiocaferacer on May 22, 2007, 05:27:29 AM

Sounds like your cam chain broke.......the twins are known for this.

Take your points and alternator covers off and see if you can rotate the cam, by turning the small bolt between the points plates. Be careful with this bolt....as it threads directly into the end of the cam. Also....try putting a 14mm wrench on the bolt in the middle of the alternator and try rotating it counter-clockwise.

If you have to rebuild the motor....dont just ditch that motor. Those early 350 twin motors are very hard to come by and if it was me....i'd rebuild it rather than put in another motor. That motor actually has a better cam profile and head to allow higher rpm's......and with that bike being so clean...keep the original motor.

Hope this helps,
Greg
www.OHIOCAFERACERS.com

also, just out of curiousity- where would you recommend looking for a cam chain?

Dave L · « **Reply #8 on:** May 23, 2007, 03:54:17 PM »

Hi
Is it possable that one of the cam bearings has siezed ie the left hand side , it may not be the cam chain .
These are not to hard to work on at all with a manuel and some good tools and a bit of space , sure looks a nice bike
dont give up
Dave

GNXFan · « **Reply #9 on:** May 23, 2007, 08:38:25 PM »

I have a 69 CL350 that I've restored(see pic) and I have many leftover engine parts if you need any. PM me for any help you may need to get that nice bike on the road.

HondaMan · « **Reply #10 on:** May 23, 2007, 09:24:28 PM »

Did you get my old 350? Looks just like it!

In the pre-1972 engines, sometimes the valve springs broke and/or the spring keepers came out, locking the engine with the valve. Check that.

mgmuellner · « **Reply #11 on:** May 25, 2007, 05:24:04 AM »

http://minneapolis.craigslist.org/mcy/336896416.html

mikedialect · « **Reply #12 on:** May 25, 2007, 11:00:43 AM »

Quote from: GNXFan on May 23, 2007, 08:38:25 PM

I have a 69 CL350 that I've restored(see pic) and I have many leftover engine parts if you need any. PM me for any help you may need to get that nice bike on the road.

that is indeed a beauty!

I will certainly keep you in mind when I end up taking it apart.

thanks!

mikedialect · « **Reply #13 on:** May 25, 2007, 11:02:46 AM »

Quote from: mgmuellner on May 25, 2007, 05:24:04 AM

http://minneapolis.craigslist.org/mcy/336896416.html

email sent!

mikedialect · « **Reply #14 on:** May 25, 2007, 11:07:33 AM »

Well, I also ruled out that I might have hydroed the engine. I had my fingers crossed, but no luck. I pulled plugs and tried to give it a good kick, but it still wont budge. However, the plugs were REALLY black and wet with gas.

I just got laid off today (yah!..?), so I might have some more time to take this guy apart in the next month. I, however, won't have the same financial backing to put it back together.

thanks again to all those who have been responding. I've been a member of other forums related to other things and this has been the most friendly/helpful out of ALL of them.

dusterdude · « **Reply #15 on:** May 25, 2007, 11:14:20 AM »

thats what we`re here for,good luck.

bryanj · « **Reply #16 on:** May 26, 2007, 04:31:42 AM »

Most spares available from www.davidsilverspares.co.uk Might be a distance but he gives good service.
Hardest thing is that to do anything to the motor it has to come out

HondaMan · « **Reply #17 on:** May 26, 2007, 08:20:51 PM »

I'm a big fan of the old CL350. I owned a couple, built a whole bunch of them for street racers, and just generally enjoyed the heck out of that motor, finally "chopping" mine for my little brother, who rode it for 6 more years after that. The only thing I would ever change about it is the carbs. Conventional slide carbs were a lot more reliable: those rubber diaphragms were the #1 source of trouble on those otherwise brilliant bikes.
I've seen them touring alongside the 500 and 750 on long trips. The only thing you had to do for that was to change the sparkplugs to #10 for the long hi-RPM duty, and they would run happily at 6500 RPM, 75 MPH, all day.

mikedialect · « **Reply #18 on:** June 09, 2007, 03:46:52 PM »

well..... I started the tear down today. And by tear down I mean started to strip the needed things- Tank (which was FULL of gas and messy as hell), exhaust (damn that scrambler exhaust is a pain!), air filters and so on... Still took several hours to get all of that off.

Anyone have any advice before I get my manual and start digging into the other stuff?

Engine removal tips?

Your best advice from where I am now?

thanks you all so far! I'm not totally confident about my abilities here, but I think that after today and reading some of your encouraging words from before has given me the gusto to at least give it a try! I'm young, dumb and right now- full of optimism.

HondaMan · « **Reply #19 on:** June 09, 2007, 09:33:05 PM »

Quote from: mikedialect on June 09, 2007, 03:46:52 PM

well..... I started the tear down today. And by tear down I mean started to strip the needed things- Tank (which was FULL of gas and messy as hell), exhaust (damn that scrambler exhaust is a pain!), air filters and so on... Still took several hours to get all of that off.

Anyone have any advice before I get my manual and start digging into the other stuff?

Engine removal tips?

Your best advice from where I am now?

Let's see if I remember....remove the tank, pipes, chain and the chain's sprocket cover, carbs, unplug wires, remove the little front mount plates, loosen the top ones and the big one in the back, then put 4 2x4s under the middle of the engine to prop it up a little. Remove the top rear bolt, then the top mounts and let the engine rest on wood, pull the big bolt (and mount plate) out of the back, and the engine falls onto the frame. Lift it a little, tilt it up at the front, and out the left side, I think. Not sure about the left side, it's been 30 years since my last 350 engine-out!

Did I forget to drain the oil? Dang.....

Spray some WD-40 or penetrating oil all the way around the cam cover's gasket: it will be REAL stuck. They always were.
Remove the screws holding the cam bearings in. (Of course, they are under other things...). Remove the tappet adjusting nuts and washers and make sure the shafts will stay in while you pull the bearings out. Pull the bearings out, trying to leave the tappet shafts in.
Remove the cam cover screws and use a stiff rubber mallet around and around to break that stuck cover off. It's a b*&$%@er...
Loosen the top head nuts from the outsides first, a turn at a time until they are all loose, then remove and lose them somewhere, that's what I often did. But, mark which ones had the copper sealing washers on them, so that when you have to buy another set, you'll at least know where they went...
Remove the camchain tensioner. Turn the crank so you can remove the cam's sprocket screws, then slide the cam out of the sprocket. Lose the sprocket down inside the engine, it's only right...you'll find it later, it's not going anywhere...
Use a wide blade or pair of wide flat screwdrivers to separate the head and cylinders. Be surprised when you see that there is lots of blowby on the pistons (always was!). That's why they burn oil when you put them into a 750 to make it an 836 engine (yep, same pistons).
Be careful whem popping loose the cylinders. That base gasket can sometimes be like the cam cover gasket.

Are you going into the transmission? There's lots more fun in there!

thanks you all so far! I'm not totally confident about my abilities here, but I think that after today and reading some of your encouraging words from before has given me the gusto to at least give it a try! I'm young, dumb and right now- full of optimism.

KeithTurk · « **Reply #20 on:** June 10, 2007, 02:20:49 AM »

This was the first motor I ever snatched out of anything... Read the manual several times... followed it and everything was just fine.... Don't remember doing anything to the motor other then looking around and painting it... but I stuck it back together and it was a lovely thing... best i can remember I was 16 at the time.

Point being... relax and have some fun... it's a fairly easy deal...

Keith Turk
200mph club Ace

mikedialect · « **Reply #21 on:** June 10, 2007, 05:28:24 PM »

Hondaman- noted!

I actually found TWO 71 cl350 engines in town here for a real reasonable price, so I'm going to go grab those tomorrow. i am going to pop this out and see if I can learn a thing or two and start the rebuild on it as I'm not sure what it's going to be just yet- although the advice and suggestions of what might have happened have definitely not gone un-noted. My manual is in the mail and I'm ecited to see this bike rolling in the future rather than sitting as an odd garage ornament.

*note the gas still under the bike- NO SMOKING in here!*

also- the exhaust mount is attached to the swing arm bolt. That should be interesting to get off...

HondaMan · « **Reply #22 on:** June 11, 2007, 06:56:44 PM »

That looks REALLY sweet.

...except that funky exhaust pipe clamp....

mikedialect · « **Reply #23 on:** June 11, 2007, 10:44:15 PM »

hehe...

well, I'm now two engines richer (pics tomorrow when it's light out). Hopefully I can pull it all off as planned (it never works that way, though- right?).

One other question...

Since the carbs on here are part of downfall- would it be wise to look for a suitable replacement? I don't want to completely bastardize the bike from it's year, but I would like some opinions in that regard.

HondaMan · « **Reply #24 on:** June 12, 2007, 08:23:24 PM »

Quote from: mikedialect on June 11, 2007, 10:44:15 PM

hehe...

well, I'm now two engines richer (pics tomorrow when it's light out). Hopefully I can pull it all off as planned (it never works that way, though- right?).

One other question...

Since the carbs on here are part of downfall- would it be wise to look for a suitable replacement? I don't want to completely bastardize the bike from it's year, but I would like some opinions in that regard.

It's really hard to beat a good-working pair of those CV carbs.....

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Author Topic: cb350 twin gurus! help needed! seized engine? (Read 13804 times)

Dave L