Author Topic: What's wrong with my bike? (Video) (Read 8753 times)

BigBoi · « **on:** February 27, 2010, 09:47:40 PM »

Background:

- Full rebuild minus the motor
- Bike starts but only when I give it gas
- Bench synched the carbs
- Bike won't run without a little throttle
- It sounds awful
- Whitish smoke from tailpipe
- Some blue smoke coming from the front of the motor
- This was the first time starting it
- Big ticking sound coming from the left hand side of the bike

I'm pretty sure I have a exhaust leak (Bad one). Don't think I installed it correctly, although I did use new crush gaskets. I torqued them more than I should have...didn't know any better.

Watch the video until the end...you can hear the ticking sound pretty clearly.

73nancy · « **Reply #1 on:** February 27, 2010, 10:04:48 PM »

check your valve adjustment.. i sent a video on here a couple months back of my 750 and the thing sounded really bad like a rod knock. what happened to mine was the lockdown nuts on the rockers back themselves out after i rebuilt the head. i would redo the valve adjustment to make sure its good. the smoke is kind of worry some but someone eles might beable to tell you what might cause that. but valve adjustment is a good place to start.. good luck

SOHC Digger · « **Reply #2 on:** February 27, 2010, 10:37:05 PM »

BigBoi:
While black smoke is overfueling, white smoke is unburnt fuel. Check to make sure that your ignition system is operating properly. If one of your coils, your points, wires, etc., are not working properly, they will cause two of the cylinders not to fire intermittenly or not to fire at all, dumping a lot of atomized fuel into and then out of the engine. Don't be mistaken in thinking you would feel a vibration if two cylinders where not firing... the CB750 is such a balanced motor that you could be running on two cylinders and unless you road tested it, you might not notice. The fact that you have to give it some throttle to keep it going further suggests the ignition circuit problem.

The blue smoke you talked about really didn't show up on the video, however, sometimes after assembly, oil on the exhaust, head, or other engine components, takes a while to cook off. It is probably not a worrysome sign unless it continues several miles after the fact.

As far as the ticking sound, I whole-heartedly agree with 73nancy on this one. Check your valve adjustment.

Keep us posted.

TwoTired · « **Reply #3 on:** February 28, 2010, 01:57:17 AM »

Ticking sound is exhaust leak at header to head.

Progressive diagnostic:
Check head pipes for even heat. Cooler ones point to cylinder issues where focus is needed.

Verify all standard tuneup items. (valve clearance, spark plug gap/ cleaned, point gap, ignition timing, air filter clean as new.)
Then vacuum sync the carbs.

White "smoke" looks like water vapor being boiled off in the muffler. (If it was fuel vapor, it would explode in the common muffler.) It may make white "smoke" until the exhaust has been at operating temp for 15 minutes or so. (It depends on how much condensation was in the pipes.)

The idle speed is set when the engine is at operating temp. Because of poor fuel atomization at cold temps, choke and throttle is needed while the motor is cold.

Cheers,

Frostyboy · « **Reply #4 on:** February 28, 2010, 04:31:48 AM »

Quote from: TwoTired on February 28, 2010, 01:57:17 AM

White "smoke" looks like water vapor

+1. If that's a recent video & you're in Canada, (I've seen how cold it is watching winter Olympics), I think that's just condensation as well. Moreso if there's a bit of choke happening there. Have you run it long enough for the muffler to get properly hot? Methinks white stuff will disappear once it's up to operating temperature.

BigBoi · « **Reply #5 on:** February 28, 2010, 06:56:07 AM »

Thanks for all the replies guys. A few more things:

Did the following (in order) yesterday before starting it:

- Cam chain tension
- Valve adjustment
- Installed exhaust

I can feel air at the number one cylinder. Definite leak. I'll have to get some more crush gaskets to check this out.

Also, all the exhaust pipes seem to be hot.

I'll report back later today.

Thanks all!

SOHC Digger · « **Reply #6 on:** February 28, 2010, 08:45:19 AM »

And I thank you TwoTired and Frostboy. I learned from this as well.

haill · « **Reply #7 on:** February 28, 2010, 10:15:37 AM »

not sure how your choke works on your bike but on mine cb500 it is somewhat counterintuitive to being on and off. gave me some troubles till realized what was happening. check to make sure your not running it fully closed which would give you some of the issues your experiencing.

BigBoi · « **Reply #8 on:** February 28, 2010, 01:08:57 PM »

I figured the choke "ON" would be towards the sky and off would be towards the ground. So I put it up when it's cold.

More news on this:

Pulled the exhaust off and put it back on. Didn't tighten the bolts as much and adjusted the sleeves a little. I'm pretty sure it's good now since it sounds much healthier. Can still really hear the cam chain though. Just so we're clear, when I adjust the cam tension, I simply have to put it to 15 degrees past TDC for 1.4 and then loosen the nut and bolt at the tensioner?

I ran it for about 5 minutes and I'm still getting white smoke out of the tail pipe and some blue smoke out of the front of the engine. I don't see any blue smoke though for the first few minutes of having it running. I still have to the hold the throttle to about 1100 for or it'll stall out.

I'm going to move it into the driveway today and run it for a good fifteen minutes to see if the white smoke subsides.

8 Track · « **Reply #9 on:** February 28, 2010, 01:21:20 PM »

I found my tach to be about 350 rpm off, so 900 was actually 550 rpm. And let me tell you, it was difficult to get that thing to idle smoothly at 550 rpm! It seems to purr at "1300".

No mention of idle jets? Are they clear? Is your float level high enough to reach them?

BigBoi · « **Reply #10 on:** February 28, 2010, 01:48:49 PM »

Quote from: twostrokecrazy on February 28, 2010, 01:21:20 PM

I found my tach to be about 350 rpm off, so 900 was actually 550 rpm. And let me tell you, it was difficult to get that thing to idle smoothly at 550 rpm! It seems to purr at "1300".

No mention of idle jets? Are they clear? Is your float level high enough to reach them?

I just finished rebuilding the carbs completely. Brand new jets all around, cleaned everything thoroughly. Set the floats to 26mm. Followed the spec for needles and jets as well.

8 Track · « **Reply #11 on:** February 28, 2010, 02:12:17 PM »

What's the condition of the battery? It won't run (very well, or at all?) below 2000 rpm with out a good charged battery.

8 Track · « **Reply #12 on:** February 28, 2010, 02:18:30 PM »

What about the little thumb screw for the idle speed? Is it there, is it adjusted correctly? I know, dumb question, but I have to ask. Also, when you synced, do you have a thread or two left at the top of the stud?

campbmic · « **Reply #13 on:** February 28, 2010, 02:36:54 PM »

I wouldn't worry about the white smoke. The rattle is definitely your first priority. I would suggest redoing your tappet clearances. I did this when I first built the bike, and it still had a knocking just like yours. I redid the tappet clearances and it was perfect! Make sure you do them super accuartely. After your done with them all test them again.

8 Track · « **Reply #14 on:** February 28, 2010, 03:37:07 PM »

It was suggested here a few years ago that the honda clearances should be opened up .001. If memory serves me right, that would be .003 intake, .004 exhaust.

As far as I know, these numbers are only for the 750.

TwoTired · « **Reply #15 on:** February 28, 2010, 04:11:29 PM »

It's going to take a looong time to thoroughly heat the exhaust idling out in the cold.
Not a lot of heat being made at idle. You need a freeway run of about 15-20 minutes at 50-70mph.

Condensation will reform every time the pipes/muffler cools off. And, one of the byproducts of combustion is water. What's the humidity like where you are? If the air is near 100%, the vapor can't really disperse quickly, as the air can't absorb much more water.

Trav-i · « **Reply #16 on:** February 28, 2010, 04:21:39 PM »

Something else to check (I found on my bike). Take your cam chain tensioner off the motor, and make sure it actually moves. I had the same problem with mine the adjuster bar inside had siezed and would not move when I loosened the bolt. I used a small drift to knock out the bar, then used some scotch brite to clean it, then a little anti-siez for lubrication. I worked it a couple of times to make sure all was well, then put it back in, and adjusted per the book and it quited right up.

Just my .02

Travis

BigBoi · « **Reply #17 on:** February 28, 2010, 04:27:08 PM »

Notes and new video:

- Checked the points today, adjusted them to spec.
- Seems to be no more blue smoke (Not sure because there's a lot of white but didn't see blue)
- Embarrassed, but the idle screw was all the way out, now it idles. $:-\$
- Still quite a bit of noise from the motor...I believe it may be the cam chain but I have no idea. Very new to this.
- Humidity in Ottawa is always high.
- One thing I noticed, is that my oil seems to be a little watery. I just put in this new oil yesterday (was none in the motor for a while, it sat...), Honda GN4 10w40. I'm going to change it again tomorrow to make sure it's kosher.

Updated video...it had been running for about 5-7 minutes at this point:

Also, unrelated note...I can't seem to get it in Neutral. There's no chain yet, that's why it's fine.

BigBoi · « **Reply #18 on:** February 28, 2010, 04:27:38 PM »

Quote from: Trav-i on February 28, 2010, 04:21:39 PM

Something else to check (I found on my bike). Take your cam chain tensioner off the motor, and make sure it actually moves. I had the same problem with mine the adjuster bar inside had siezed and would not move when I loosened the bolt. I used a small drift to knock out the bar, then used some scotch brite to clean it, then a little anti-siez for lubrication. I worked it a couple of times to make sure all was well, then put it back in, and adjusted per the book and it quited right up.

Just my .02

Travis

How much trouble is it to get off and then back on?

Trav-i · « **Reply #19 on:** February 28, 2010, 04:32:34 PM »

None at all. First remove the starter cover (2 small bolts). Then remove the 3 bolts that hold the adjuster on (1 on top 2 on the bottom), just make sure you are careful with the gasket. Once it's off you should be able to push the adjuster with your fingers, and it should slide smoothly. If not then a simple clean up is in order. This has helped quiet 2 bikes i have worked on.

Good Luck

Travis

8 Track · « **Reply #20 on:** February 28, 2010, 05:47:19 PM »

You're right, it doesn't sound right, just sounds like tuning. Have you listened to any cb's on youtube to get an idea of what one sounds like? If not, here's mine, not quite warmed up, clutch basket rattle and all, a la blackberry.

BigBoi · « **Reply #21 on:** February 28, 2010, 06:23:41 PM »

Also, further to my comment about oil above. About 20 minutes after I shut off the bike, I opened the oil tank to check the oil again and there seemed to be some smoke coming out of there. Not a lot, but enough for me to notice. How would water possibly get in there to evaporate?

One more note I want to add to this is my carb settings.

It's a K2 750 bike, but I got a replacement bank of carbs. A set of 069a.

I used the stock needles from my previous carbs (K model), and replaced the rest with:

110 Jets
40 Pilots
26mm float height
1 turn on the air screw

Bench synched to 1/8 bit.

I'll do a real synch later this week when my Morgan comes in.

8 Track · « **Reply #22 on:** February 28, 2010, 06:47:17 PM »

Sounds like what you've got is correct, or close to, but the air screws might need to start at 3/4 turn. You'll probably end up at 7/8 turn. Yours sounds like it's running heavy on two cylinders. Hear how it sounds like a vertical twin? Make sure your points are set correctly. Many will tell you to get rid of them. Read your plugs. Remember it's harder to jump a larger gap; I set mine at the small side of the normal range. If I remember correctly, the manual calls out for a plug that many have discovered is a little cold. If you're having fouling problems, do a search on that.

I went through my carbs with a fine tooth comb a few years ago. I didn't trust float height, so I measured volume. I pin drilled jets to put me in the ballpark, then bought the correct jets. I drilled my emulsion tubes. I messed with needles. If there was something to tweak, I did it. My problem turned out to be the needle bushings were worn out- I was dealing with a 1/16 throttle choppiness.

I set my points with a dwell meter and they are spot on.

You've got it running, that's a start. Now you have to give it a tune up. Let the fun begin!

8 Track · « **Reply #23 on:** February 28, 2010, 06:51:51 PM »

The oil... Is it hot? Is it just vapor? Water is a byproduct of combustion and you may be seeing a little vapor in your tank. Mine does it too. How cold is your garage while you're doing all of this?

BigBoi · « **Reply #24 on:** February 28, 2010, 07:30:19 PM »

Quote from: twostrokecrazy on February 28, 2010, 06:51:51 PM

The oil... Is it hot? Is it just vapor? Water is a byproduct of combustion and you may be seeing a little vapor in your tank. Mine does it too. How cold is your garage while you're doing all of this?

It's about 5-10 degrees in there if I was to guess. (Celsius)

It looked like vapor because it didn't have a thick smell to it. I'm not sure how hot the oil was at that point, I'll check again next time.

News:

Author Topic: What's wrong with my bike? (Video) (Read 8753 times)