Author Topic: Engine stuck while driving (Read 9557 times)

killersoundz · « **Reply #25 on:** May 05, 2012, 03:54:24 PM »

Quote from: MoMo on May 03, 2012, 09:15:37 PM

Quote from: killersoundz on May 03, 2012, 08:23:34 PM
Related question: How do we know the engine is getting proper oil? Is an oil pressure gauge enough?

An oil pressure gauge only tells you that the pump is working and pushing enough oil into the lower oil galley. Running the motor for a short while with the valve caps off should provide visual info as to oil getting from the lower galley up through the passages and on to the top end...Larry

Thanks for the tip. I'm rebuilding a barnyard 750 engine that I've never seen run. So I'll need to do this to verify it's getting oil to the top end even if the oil pressure gauge I'm putting on says it has pressure.

jester · « **Reply #26 on:** May 05, 2012, 04:43:57 PM »

Ok, progress!! got the engine out and the valve cover off. The bolts were rusted and had to drill 7 of them out. gonna order a new set and gasket when i know the problem. So, the valves look pretty clean as far as I know. A thing I noticed though is a lack of oil on the right side of the camshaft. The springs and valves were pretty oily. I guess I have to dig deeper and take the valves off. This is my first time doing this. should I pay attention to something in particular while doing this or will just following the manual suffice? Someone mentioned labeling is important to put everything back together afterwards, so i'll do that.

killersoundz · « **Reply #27 on:** May 05, 2012, 05:48:07 PM »

Ouch about drilling out your valve cover screws. Tip - you need a #3 Phillips bit. My bike was as rusty as they get and they still came off relatively easy except I did tear up the head of one of them.

The cam looks super dry even kind of dusty on the right side, not good.

When I take the head apart I get 4 zip baggies, label them for cylinder 1,2,3,4 and separate the rockers and cam bearing pieces corresponding to their location so they can be installed back in the same place. I put the rocker shafts back in as they don't get in the way. To pull the head off you will need to take the cam towers all the way off and remove the rubber pucks because there are 4 more bolts hiding under there don't forget those!

That right side definitely looks like it had an oiling problem to me, notice how even the top of the springs are a little more rusty looking

Roach Carver · « **Reply #28 on:** May 05, 2012, 09:25:47 PM »

Cam towers on the right look discolored. Pull the cam and see what you find. I bet it will turn over once the cams out. DO NOT DROP THE CAM CHAIN.

DedHed · « **Reply #29 on:** May 06, 2012, 07:55:52 AM »

Looks like someone done stuffed paper towels in the intake.... That'll do it everytime.....

Watching this one...
Good luck,
Phil

jester · « **Reply #30 on:** May 06, 2012, 11:49:57 AM »

Yeah, I stuffed all the holes on the engine. Ok, bad luck, i wanted to take the cam chain off but the since the engine is stuck one of the hex nuts on the cam chain sprocket is unreachable. I have to get a small wrench. In the mean time i decided to get the plugs out, but one of the plugs broke in half while twisting it out. Don't know how i'm gonna deal with thisone...

killersoundz · « **Reply #31 on:** May 06, 2012, 12:48:14 PM »

I'll cut to the chase it's looking like you'll need a new head for the engine very likely. I also had a seized engine with the same issue, where one of the bolts on the cam sprocket was in that same spot you can't get to. I BET you can get the engine to turn over enough to get to that bolt. Take the stator cover off, and put a 20mm socket on that crankshaft bolt (IIRC) and get a big breaker bar and try to turn it. I got my engine unstuck pretty easily that way

jester · « **Reply #32 on:** May 06, 2012, 04:43:58 PM »

OK, thx Killersoundz, you were right, i got the biggest wrench i got on the crankshaft bolt and it turned over. So it was definitely an oil shortage on the right side of the camshaft. How does this happen? I don't know how oil gets distributed in this engine. Should I check for a clog somewhere? Was my oil pressure too low? As you can see on the pictures, the cam shaft holder(don't know the name of this part) is scratched. I'll have to order a new one. Should I also order a new camshaft or you think this one is still fine? The pistons go up and down fine. Maybe new rings while i'm at it, cuz i think this is the first time this engine has been opened (49000 miles). What does everybody think?

killersoundz · « **Reply #33 on:** May 06, 2012, 04:51:48 PM »

It looks like the bearing surfaces on both the cam towers and the camshaft are pretty tore up. You'll probably have an easier time just finding a whole SOHC head on ebay, which you could then decide if you want to use that replacement head or switch some things around. I would replace the piston rings while you're at it.

MoMo · « **Reply #34 on:** May 06, 2012, 06:28:56 PM »

Cam and tower need to be replaced. Are you sure the motor has never been apart? Bits of silicon/gasket sealer can plugs the passageways and cause what you are seeing...Larry

MCRider · « **Reply #35 on:** May 06, 2012, 06:56:56 PM »

Quote from: MoMo on May 06, 2012, 06:28:56 PM

Cam and tower need to be replaced. Are you sure the motor has never been apart? Bits of silicon/gasket sealer can plugs the passageways and cause what you are seeing...Larry

Agreed, I've seen and heard of a lot of cam seizures. Including one of my one. NEVER on an engine that hadn't been apart, introducing debris to the system, usually silicone sealer.

As to dropping the cam chain that's the least of your worries, and not really an issue. Easy to fish out with a magnet.

If you have to you may have to cut the cam chain with a small grinder. But I'd try to get the cam to turn by hook or crook. Don't manhandle the nut on the ignition side, its not up to it.

If you have to go Roman on it, take the alternator cover off and use the nut on that side.

CycleRanger · « **Reply #36 on:** May 06, 2012, 07:51:16 PM »

Quote from: jester on May 06, 2012, 11:49:57 AM

In the mean time i decided to get the plugs out, but one of the plugs broke in half while twisting it out. Don't know how i'm gonna deal with thisone...

Aw jeez, that's tough! I recently had that happen with my XL250s head.
It took much careful drilling, filing, and chasing to rectify the problem.

jester · « **Reply #37 on:** May 07, 2012, 05:36:55 AM »

The motorcycle is a cb750 k6 '78. I'm looking on ebay now to find some replacement parts. can i use the towers and cam of previous models/hondamatic or does it need to be the 78 model? I found these: http://www.ebay.com/itm/1976-HONDA-CB750-CAMSHAFT-HOLDER-/230769444783?pt=Motorcycles_Parts_Accessories&hash=item35baee47af&vxp=mtr#ht_2815wt_1163
http://www.ebay.com/itm/HONDA-CB750A-HONDAMATIC-CB-750-CAM-SHAFT-/160796128282?pt=Motorcycles_Parts_Accessories&hash=item257032341a&vxp=mtr#ht_1056wt_1163

Thx

SOHC Digger · « **Reply #38 on:** May 07, 2012, 06:24:03 AM »

Quote from: jester on May 07, 2012, 05:36:55 AM

The motorcycle is a cb750 k6 '78. I'm looking on ebay now to find some replacement parts. can i use the towers and cam of previous models/hondamatic or does it need to be the 78 model? I found these: http://www.ebay.com/itm/1976-HONDA-CB750-CAMSHAFT-HOLDER-/230769444783?pt=Motorcycles_Parts_Accessories&hash=item35baee47af&vxp=mtr#ht_2815wt_1163
http://www.ebay.com/itm/HONDA-CB750A-HONDAMATIC-CB-750-CAM-SHAFT-/160796128282?pt=Motorcycles_Parts_Accessories&hash=item257032341a&vxp=mtr#ht_1056wt_1163

Thx

It's either a K6 (1976) or a K8 (1978), not both.

The cam and cam towers cross over for certain years, but not all. I use www.cmsnl.com and cross reference part numbers to see what years had the same parts.

MCRider · « **Reply #39 on:** May 07, 2012, 06:38:20 AM »

Even thought the cam towers have differences, I think they could all be interchangeable. So I think the bearings in your ebay lisitng would work.

I can't see where an "A" cam would work in a K, as it was a 2 speed motor with much different characterisitcs. I'd look for a K cam.

Elan · « **Reply #40 on:** May 07, 2012, 05:47:22 PM »

just found this...

http://www.ebay.com/itm/Honda-CB750K-CB750-1978-Cam-Towers-/330726248134?pt=Motorcycles_Parts_Accessories&hash=item4d00d20ec6&vxp=mtr#ht_1264wt_1144

jester · « **Reply #41 on:** May 07, 2012, 08:01:39 PM »

nice 1 Elan, just ordered it

Grabcon · « **Reply #42 on:** May 07, 2012, 08:32:41 PM »

Sorry about your unfortunate issues. Sometimes when it rains it pours.

But just a thought while you have it apart. In the back of Hondamans book there is a section called Cheap Top End Improvements (low cost and no cost performance enhancements). In this section it talks about adding extra oil holes to the cam blocks, and doing some mods to the rocker oil holes. Although I have not got my motor back together to see what improvements these mods made the effort was all of 30 minutes.

jester · « **Reply #43 on:** May 08, 2012, 10:45:48 AM »

Thx Grabcon. Is this what you mean; http://www.sohc4.net/?p=294

Grabcon · « **Reply #44 on:** May 08, 2012, 06:24:04 PM »

Not exactly. Hondaman describes in his book putting additional oil hole on top of the cam block in strategic locations. I would scan a copy of the photo but I don't want to get in trouble since he lives by me.

This provides much needed lubrication from the top side.

Elan · « **Reply #45 on:** May 08, 2012, 06:29:35 PM »

Quote from: Grabcon on May 08, 2012, 06:24:04 PM

Not exactly. Hondaman describes in his book putting additional oil hole on top of the cam block in strategic locations. I would scan a copy of the photo but I don't want to get in trouble since he lives by me.

This provides much needed lubrication from the top side.

here it is, from the man himself...

http://forums.sohc4.net/index.php?topic=59423.0

lucky · « **Reply #46 on:** May 08, 2012, 07:03:41 PM »

Engines seize because of lack of oil and then they get hot.
Engines seize because the get hot from incorrect timing.

Aatrain · « **Reply #47 on:** May 08, 2012, 07:37:57 PM »

I heard from a triumph dealer that the little oil passages to the top were prone to getting plugged up pretty easily and that lead to alot of overheats and seizures. That was one thing he told me to be aware of when I was looking for a replacement engine. Would this be a) true; and b) a possibility for this lock-up? I'd like to know the validity of this claim from the trump guy...
Good luck getting that going again

MCRider · « **Reply #48 on:** May 08, 2012, 08:42:28 PM »

Quote from: Aatrain on May 08, 2012, 07:37:57 PM

I heard from a triumph dealer that the little oil passages to the top were prone to getting plugged up pretty easily and that lead to alot of overheats and seizures. That was one thing he told me to be aware of when I was looking for a replacement engine. Would this be a) true; and b) a possibility for this lock-up? I'd like to know the validity of this claim from the trump guy...
Good luck getting that going again

That is likely what happened here. The result of one or both of the oil orifices getting plugged is a cam seizure.

However, i take issue with the use of "prone" I have never heard or seen of any CB750 seizing a cam that had never been apart.

The orifices get plugged with debris, usually the misuse of silicone sealer, from a tear down. That's not the engines or Honda's fault.

The thing to be aware of in buying a used CB750 is, has it been apart. If so, look closely for evidence of silicone sealer. It will ooze out of the gasket place and harden. It oozes on the inside as well as the outside. On the inside, little bits of the hardened silicone break off and travel like a blood clot looking for a restriction, and they find it in the oil orifices feeding the cam.

If it has been apart and back together and you can't see any silicone, still request that you remove the pan and look at the oil pump screen. It too will collect bits of silicone.

jester · « **Reply #49 on:** May 09, 2012, 07:27:19 AM »

So if i'm putting the engine back together, what do i do to seal the gaskets in the best possible way? And I ordered the towers Elan found on Ebay. Should I do the oil mod or not? What are your recommendations? Still looking for a camshaft though.. Found some k4 ones, they look the same, except for the cam chain sprocket, which, in 74', didn't have holes in it. Is it safe to use one of those on my 78' bike?

Thx

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Author Topic: Engine stuck while driving (Read 9557 times)