CL-350 rebuild. Exhaust smoking. Normal?

T

theunfrailhale

New Member
Just want to share a quick video and get some input on this motor rebuild.

http://www.youtube.com/watch?v=V1OxK2kMOnM&feature=youtu.be

Firstly I am proud to say this is the first motor that I have ever had down to the guts and back that I was able to make run.

I have been reading my manuals about carb tuning, and it says to let the motor run for 5 minutes before fiddling with stuff. About 2-3 minutes into running, I start to get a bit of smoke out of the tailpipes. Its Monday, and the first time this was fired up was last Thursday, so it has been run for maybe a total of 30 minutes, probably less... Is that smoke normal for a new engine? Is it just the piston seals getting situated, or did I neglect to change the copper valve guides when I should have?

anyways, check out my motor. Let me know what you think... I welded up this bench rack and slapped some plates together to test it all. I wanted to make sure the motor was going to be functional before I started pouring my heart into the rest of the bike... Happily, I think she's gunna work, even if I need to rebuild the top-end again...

Thanks for any feedback.
 
Do a compression test. If it flunks the compression test, then you flubbed the engine rebuild. Then you would do a leakdown test to determine where is it losing compression.

If it passes the compression test, then you are probably getting oil past the valve stem seals. That's not bad unless it is excessive, which would cause an unpleasant amount of smoking and carbon build-up.

New rings, properly installed, seat pretty well right from the get-go, and there should be no smoking. Have you ever seen a new motorcycle or car that smoked?

What was your ring end gaps when you put it together?
 
Yeah, ran the compression test. 90 on the right, and 100 on the left. Pretty shitty if I'm going by the book. So, time to look into the leakdown test, though, I took the jugs to a machine shop, one that was reputable and by my estimate all the work they did was quality, and they bored and honed to match my new pistons. So unless i really fouled up the ring install, I am guessing its valves.

I did a rough valve job with some lapping compound, and used a die grinder to de-carbon my valves. I sense a lot of room for error there, and tbh, I might not even have oil seals on my valves.

This is what happens when you have no idea what you're doing and you take two years to do it... first time blues I guess.

SO, leakdown test will be googled and I'll proceed there, and then prob buy some new valves and guides/seals. Is it worth paying a shop to do a valve job? e.g. that machine shop had the ability to put like a three angle cut or programmed radii on the valve seats. or should I look into cutting my own with one of those valve seat resurfacing tools?

Thanks for the reply.
 
Don't do it yourself. You obviously don't know what you are doing. Do you even have the service manual?
 
ask them to show you the bore gauge in the cylinder when the work is done next time, usually if they're a good machinist, they get all red and giggly because they want to show off how well they hit the number, if they shrug it off then chances are your job was finished with a "close enough for the shit we do" and sent out the door. I'm a little inquisitive about the "die grinder" used to decarbon the valves too, imo a die grinder shouldn't even be on the same workbench as valves, if you're talking about a dremel with a brass brush wheel then that would be less scary. where did you get your lapping compound btw? if you got it from the auto store down the street, toss it, that stuff is too coarse to use in these bikes and will leave you with a shit seal, goodson sells a "coarse" and "fine" compound and is the only type I use, I rarely use the coarse either, if you need it, you probably need the seats and faces cut.
 
I absolutely don't know what I am doing, I have recently acquired a copy of the FSM, but until then I have been referencing my Clymer. I realize that there are certain things that are bad form, and things that you can fudge. Unfortunately all of these arent explicitly written down, and are either gained by having a friend/father/mentor that knows whats up or, experience. Unfortunately I'm on my own here aside from the support here on this site.

Fortunately, I retested my compression, with the throttle open this time, and I am sitting at 130psi per cyl. Not the 170 that the clymer calls for, but a shit-ton better than the 90/100 I was getting.

As for valve jobs, I was wondering if any have experience with those valve seat cutters that have the dowel down the center.. It sounds like I'm best off getting them cut at the shop anyways.

I used a pneumatic die grinder on the flat-dish of the valve that faces the combustion chamber, and a light bit arount the conical "funnel" part. For abrasive I used cut up squares of scotch-brite pads. Its comparatively low abrasive and I avoided the valve seats all-together. I mounted the scotchbrite by cutting them into 2" squares, and then stacking 4 or 5 of them and putting them on a spindle used for cotton-polishing wheels. I used to work sheet metal, and scotchbrite was a common fine-abrasive used it the polishing process.

As for the burning oil, I don't think I put on oil-seals over my valves :-[ :-[. I know this probably makes you wanna punch me in the face, but these "common sense" things are common if working on engines is something you have commonly done. Yes I RTFM, but its been 2 years since i started this project, some things slipped my memory when I decided to just get this piece put together. Fortunately I have only run the engine for a few minutes at a time, and for less than 30 minutes all together. I avoided finishing this project because I was afraid of making a mistake. Its been a two-year protracted process, and the fact that I didn't send a valve through my piston, and that the engine fires and idles is a huge victory for me in itself. A top end rebuild is only an afternoon project so, I am not too worried about that teardown, especially if I am going to have the valves replaced and the seats cut.

As for lapping compound, yeah, the stuff from autozone. my buddy that *has* rebuilt car engines picked it up and made the suggestion. Since I am going to look at getting valves replaced/seated, I'll not worry about doing another lap, but for future builds, what would you suggest?

Now, i'll finish this with a couple questions.

What kind of PSI should I expect real-world after a rebuild? Are you getting 170 after an experienced rebuild?

The cylinders are bored over .5 thousandths, is that increased displacement going to affect my compression? I think I calculated the volumetric difference from stock 325cc to 331cc...

Is it worth paying for a performance valve cut on a stock-er type engine?

Sorry for all the face-palms I am surely causing. I do appreciate the feedback.
 
theunfrailhale said:
As for the burning oil, I don't think I put on oil-seals over my valves :-[ :-[. I know this probably makes you wanna punch me in the face
Click to expand...

You are being way too hard on yourself.
Doing a valve job is for a machine shop or an experienced mechanic. You are neither. Take your heads and have them done for you. Make sure you give them the valve stem seals. <G>
 
^ =/ that makes me feel a bit less spaced. I was looking at these and thats when I realized I didn't put valve seals on...

http://www.ebay.com/itm/HONDA-CB350-CL350-SL350-CB360-BRONZE-VALVE-GUIDES-WITH-VITON-SEALS-/231002865213?pt=Motorcycles_Parts_Accessories&hash=item35c8d7fe3d&vxp=mtr

maybe I will get these since it appears I need some valve/valve-guide work anyways...
 
I actually got a complete valve job from him using those guides, great guy. Excellent service and quick turnaround
 
nice! I need to wait for some paychecks to stack up, but it looks like getting my valves worked will pay off in the long run. I might end up doing the cam roller-bearing conversion at the same time... Something about the cam-carriers in the 350 just don't make me feel at ease...
 
Don't waste your money on the cam bearing conversion. I race a stock engined CB350 and they work just fine as they are.

theunfrailhale said:
nice! I need to wait for some paychecks to stack up, but it looks like getting my valves worked will pay off in the long run. I might end up doing the cam roller-bearing conversion at the same time... Something about the cam-carriers in the 350 just don't make me feel at ease...
Click to expand...
 
Yup no valve seals on the 350.
Is there a chance you installed the rings upside down?
They should have a "T" or something stamped into the top surface of each, that would cause smoking and oil burning if they were upside down.
Do a quick leakdown test before you go and disassemble and pay to have anything done.
Get a compressor with a rubber nozzle and spray about 100-120 psi into the spark plug hole. (make sure you have the engine secured at TDC where it cannot turn) and listen for leaks. If you have one you'll know it.
 
Eight40 said:
Don't waste your money on the cam bearing conversion. I race a stock engined CB350 and they work just fine as they are.
Click to expand...

i agree,no exp. racing one here but i have flogged my 350 for 10.000 trouble free miles so far.... i think it is a really good design,stock, better than the 360 cam in head i figger
 
Leakdown test it is. Thanks for all the feedback.

I had to replace the original cam and camriders due to serious meltdown on one side, so thats why I was considering the conversion... The bit of reading I was doing last night suggested that one cause of cam melt-down is the oil plunger wearing out... I did check that for excessive play and it was within spec... Is there a good way to check oil pressure on the 350?
 
There's a small bolt on the left side of the cam box, above the left cam cover. Remove it after starting the engine. You should have oil coming out of it.

(edited exact location of oil pressure test port)
 
SONICJK said:
Yup no valve seals on the 350.
Is there a chance you installed the rings upside down?
They should have a "T" or something stamped into the top surface of each, that would cause smoking and oil burning if they were upside down.
Do a quick leakdown test before you go and disassemble and pay to have anything done.
Get a compressor with a rubber nozzle and spray about 100-120 psi into the spark plug hole. (make sure you have the engine secured at TDC where it cannot turn) and listen for leaks. If you have one you'll know it.
Click to expand...

that's a bit dangerous, a leakdown test at 5 psi is just as effective and won't hurt you if the piston gets free
 
Roc City Cafe said:
that's a bit dangerous, a leakdown test at 5 psi is just as effective and won't hurt you if the piston gets free
Click to expand...
Probably true.
But it's a lot easier to hear the leak at 120 without a stethoscope ;)
 
If I am going to continue to do my own engine work, I may as well get some tools to do it accurately. I don't really have a problem with spending money on tools.

The harbor freight leakdown tester has some poor reviews, this one however seems to be pretty popular.
http://www.amazon.com/OTC-5609-Cylinder-Leakage-Tester/dp/B0030EVL60/ref=sr_1_1?ie=UTF8&qid=1374958591&sr=8-1&keywords=leak+down+tester

So that, and my own compression tester, probably good tools to have on hand. (?)

This is a "lets make an engine work" experience for me. This is the first time I have made a motor fire, so despite all these setbacks Im pretty damn happy so far about what I have learned. After I go through my paces with this motor and get it as proper as I can, I intend to pick up another spare 350 motor and do a performance motor with the oil-pump mods, oil cooler, forged pistons yada yada.

Im in my sophomore year in engineering school, and we have options for vehicular based senior projects, so I feel like expenses are more or less investments in understanding.

that's a bit dangerous, a leakdown test at 5 psi is just as effective and won't hurt you if the piston gets free
Click to expand...
what do you mean here? like, if I build up enough pressure to move the motor? what kind of damage would that cause?
 
Eight40, thanks for that info. I'll have to check that out when I get home... Maybe I can even figure out how to install a pressure gauge somehow...
 
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