Author Topic: Camshaft and timing question (Read 3440 times)

Longfellow · « **on:** January 29, 2013, 06:29:13 PM »

CB650 = R10
CB550 = R11

Is this correct?

I've looked over every single cam swap thread I could find, but I couldn't ascertain what they are marked. I already have the bike back together so I can't measure the lobes at the moment. I'm having an engine timing issue with my CB550 engine, and believe the previous owner stuck a CB650 (it's marked R10) camshaft into it. If that is the case I'm fairly sure it needs to be degreed because as far as I can tell it's timed correctly going by the marks, but the intake valves are closing just slightly to late.

Any help would be appreciated.

dave500 · « **Reply #1 on:** January 29, 2013, 07:14:28 PM »

ive seen 500/550 cams with r10 r 12on them,are you using a degree wheel?

crazypj · « **Reply #2 on:** January 29, 2013, 07:26:37 PM »

Pistons in backwards?
Exhaust cutaway is smaller than intake

Longfellow · « **Reply #3 on:** January 29, 2013, 07:32:40 PM »

I was planning on using a degree wheel and dial indicator.

My main issue is that when I install the vacuum gauges to synchronize the carbs, the needles are fluctuating from 10-15psi to -20 in/hg. So it seem the intake valves are closing just slightly to late and some of the compression stroke is being forced back into the intake system.

I also pulled the intake system off and rotated the engine and I can visually see the intake valves are still slightly open on the compression stroke according to the timing marks.

Longfellow · « **Reply #4 on:** January 29, 2013, 07:36:00 PM »

I re edited my first post. The intake isn't opening to early; It seems that it is not closing all the way on the compression stroke, which is causing it to force air backwards into the intake just slightly.

And the pistons are in the correct way. The bike runs pretty decently and has no issue driving around, I just can't get a steady vacuum reading to synch the carbs and I'm worried that on prolonged running it might over heat the cylinder head.

goldarrow · « **Reply #5 on:** January 29, 2013, 07:55:49 PM »

Check out my build thread on page 5.

The 650 cam marked R10 L. My stock 550k1 cam marked R10 J.

crazypj · « **Reply #6 on:** January 29, 2013, 08:11:15 PM »

Did you skim head or block?
That will retard cm timing.
About 8~10 degrees for 0,020" (thinner head and base gaskets can have same effect)

Longfellow · « **Reply #7 on:** January 29, 2013, 08:13:47 PM »

I'll pop the rocker cover off and check then, thanks for the info. I'll probably take the cam out and measure it just to be sure.

I think I'm going to need an adjustable sprocket to solve my problem. The timing chain didn't appear to be overly loose, and the tension unit is working fine.

Like I said, the bike runs pretty well, just want to get around to synching the carbs and getting the air mixture dialed in.

Longfellow · « **Reply #8 on:** January 29, 2013, 08:16:11 PM »

Quote from: crazypj on January 29, 2013, 08:11:15 PM

Did you skim head or block?
That will retard cm timing.
About 8~10 degrees for 0,020" (thinner head and base gaskets can have same effect)

Good question, I didn't build this motor so I'm not totally sure, there's a possibility that it could have one or both of those. I was told it had a 605cc bore kit, pod filters, full exhaust, and 120 main jets. The intake valves are clean and so are the intake ports. The exhaust ports have mild carbon build up, but nothing more than normal.

The more I research the issue it looks like I'll either have to completely tear apart the engine (I'd like to avoid that,) or try an adjustable cam gear.

crazypj · « **Reply #9 on:** January 30, 2013, 12:13:47 AM »

Check cam timing, the sprockets are not hardened, you can use a chainsaw file to slot the mounting holes

dave500 · « **Reply #10 on:** January 30, 2013, 12:18:03 AM »

have you got damper valves on your vac guages?if not they will jump all over the place.

Longfellow · « **Reply #11 on:** January 30, 2013, 08:51:49 AM »

Not sure about the damper valves. I can physically feel a pulse in the hose when I have the gauges mounted to the intake runners.

dave500 · « **Reply #12 on:** January 30, 2013, 11:25:57 AM »

the damper valve is fitted inline with the vacuum hoses,it reduces those pulses as you wind the knobs on them down,if you dont have them your not doing it correctly,heres a set with adjustable damper valves.

Longfellow · « **Reply #13 on:** January 30, 2013, 05:03:54 PM »

The lack of a damper valve on the gauge turned out to be the issue. I've never dealt with motorcycle engines so I had no idea that the valve over lap would cause that issue with the gauge not having a damper valve. The only thing that made sense to me (damper unknown) was that my cam timing was off.

Thanks for all the help, really appreciate it.

crazypj · « **Reply #14 on:** January 30, 2013, 08:44:36 PM »

Get some 45 pilot jets and push them into the vacuum line, it smooths things out

Longfellow · « **Reply #15 on:** January 30, 2013, 10:12:48 PM »

I just bought 4 inline fuel shut off valves from autozone. Worked perfectly.

crazypj · « **Reply #16 on:** February 02, 2013, 06:35:43 PM »

Doesn't everyone have a box of old pilot jets?

dave500 · « **Reply #17 on:** February 02, 2013, 08:32:34 PM »

everyone with pods does.

bjatwood · « **Reply #18 on:** February 07, 2013, 04:40:50 PM »

Quote from: dave500 on February 02, 2013, 08:32:34 PM

everyone with pods does.

LMAOFF!!

MRieck · « **Reply #19 on:** February 07, 2013, 06:27:24 PM »

Quote from: dave500 on February 02, 2013, 08:32:34 PM

everyone with pods does.

Nobody likes a hater

dave500 · « **Reply #20 on:** February 07, 2013, 11:59:50 PM »

im not a hater,,in fact i hate hate,hate it!

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Author Topic: Camshaft and timing question (Read 3440 times)