Author Topic: Motor locked up today. What's next? (Read 5598 times)

wrenchmuch · « **Reply #25 on:** March 28, 2010, 01:33:17 PM »

Are all the other fasteners on that side tight ? Bearing caps and the 2 ,10 mm bolts in the center front and back are what hold the cam holder down . If the cam holder lifts from the head pressure is lost to the bearings . If the remaining fasteners are tight then I would bet you have blockage on that side or you might be missing the outer o-ring under the cam holder . There are two o-rings under the cam holder . The inner ones seal the oil supply to the head and the outer ones seal a second oil supply hole to the holder . This is where oil would enter if the holder was on the other side of the head .Oil pressure in the holder might drop without the outer o-rings . When you get the cam and holders out you will see the oil feed in the head . On your year a little jet lifts out of the head . You might find your blockage here . This happened to me two seasons ago . Took the bike out for 20 min and it died at a light after a short squeal . 10 min later it started and got me home . I was missing the outer o-rings under the holder and when I stripped the engine I found a lot of silicone where the sleeves meet the barrels after someone in the 70's installed a 895 cc kit . Mine is a k1 and the oil jet is not removeable so I never did completely confirm the cause . I ended up rebuilding the engine . You could probably get away with just replacing the damaged parts in the head and new rings if you end up pulling the barrels but you need to clean out that engine in case it was a blocked oil passage . It would suck to replace the damaged cam parts just to have it happen again from missed garbage in the oil passages . Don't forget the tank when you clean . It was real bad in there . The good news is I bet your pistons are fine and the bearings and rockers should be easy to find and relatively cheap on ebay . Someone around here cam help with a cam .
Hope this helps
Mike

fire113 · « **Reply #26 on:** March 28, 2010, 01:37:37 PM »

...change the towers complete and You can save Your head.
Here is a pic of My head without the towers & co.

wrenchmuch · « **Reply #27 on:** March 28, 2010, 01:48:23 PM »

How about this ?
http://cgi.ebay.com/ebaymotors/Honda-CB-750-Camshaft-and-cam-tower-assembly-complete_W0QQcmdZViewItemQQhashZitem1e5b1acf84QQitemZ130377502596QQptZMotorcyclesQ5fPartsQ5fAccessories

fire113 · « **Reply #28 on:** March 28, 2010, 02:40:52 PM »

...this price and 7 day money back sounds good. Be sure that it is the right model.
Not sure but I think some oil holes are different from model to model.

Yamanube · « **Reply #29 on:** March 28, 2010, 04:42:58 PM »

Quote from: fire113 on March 28, 2010, 02:40:52 PM

...this price and 7 day money back sounds good. Be sure that it is the right model.
Not sure but I think some oil holes are different from model to model.

Can anybody confirm or deny this?

How about these parts?
http://cgi.ebay.com/ebaymotors/CB750-SOHC-camshaft_W0QQitemZ250601729990QQihZ015QQcategoryZ35595QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Also, can an F cam be used in a K motor?

wrenchmuch · « **Reply #30 on:** March 28, 2010, 05:42:18 PM »

My understanding is that all cam towers are interchangeable through the years including automatics . You will find 2 kinds . Those that have a bolt next to the rocker that stops the rocker shafts from turning and those that don't . My k1's don't . This is a mod that came in later to reduce valve train noise ( see thoughts of Hondaman in the FAQ section for more info on this ). Any you see are good in your motor . Just be sure that they have the caps . I've seen auctions that don't have caps

Cams changed through the years . The best of them are from the early years .They made the most power . I went with a new cam ( Webcam #41 ) when I rebuilt . It was about $200.00 .Either of the ebay cams would work fine in your motor.
Mike

Yamanube · « **Reply #31 on:** March 28, 2010, 06:02:24 PM »

Sorry, what caps do I need? And thanks all for the information. Hopefully I can get the parts I need then jump back on here and bother you guys with a million more questions about how to put it back together.

wrenchmuch · « **Reply #32 on:** March 28, 2010, 07:00:53 PM »

I just ment the bearing caps . They are bored together with the cam holders so only the caps that came with that holder will fit . I have seen auctions where the holder didn't come with the bearing cap . Makes the holder useless . The cap is the piece you took off in your 4th image too expose the cam bearing surface .

Yamanube · « **Reply #33 on:** March 28, 2010, 07:24:53 PM »

I won the auction that I posted up there ^^ comes with bearing caps. Does it seem like a decent deal? Should be what I need as far as valve train correct?

Also based on the pics I posted would the motor likely have stuck due to not enough oil to the cylinder and the piston stuck or due to the cam siezing up and dragging the rest of the motor down via the cam chain?

wrenchmuch · « **Reply #34 on:** March 29, 2010, 03:47:21 AM »

The cam seizing can stop the engine . I'm pretty sure nothing happened to your piston as a result of the cam seizing . Thats a great deal on the cam , rockers , and cam towers .
Mike

Yamanube · « **Reply #35 on:** March 29, 2010, 06:45:35 AM »

What do you guys think of the cyclexchange.net gasket kit? It seems complete and a great price.
Also, if the cylinders end up looking good, what other things should I do while I have the motor apart? New valve guides? Hone and rings? The bike has about 18k miles.

wrenchmuch · « **Reply #36 on:** March 29, 2010, 02:42:07 PM »

I have used the cycle x kit and am happy with it . Honda gaskets are better but more $ . If you are planning to pull the cylinders off then you should probably count on at least a hone and new rings but you should look at the condition of everything first . I would think your guides would still be ok after 18000 mi . Get everything apart and cleaned and then see what you have to work with . Look at all the guides and tensioners . They have rubber parts that can harden over time . New ones are fairly pliable . When they get hard chunks can break off . Its easy to spend a lot of money on these things .
Try and decide early on how far you want to go .
Mike

Yamanube · « **Reply #37 on:** March 29, 2010, 05:51:59 PM »

Somebody mentioned if I was pulling the head to plan on pulling the cylinders to replace the base gasket because it will leak. I don't really want to do more than I have to but I ordered a complete gasket kit in addition to the valve train parts from ebay.

bistromath · « **Reply #38 on:** March 29, 2010, 05:58:46 PM »

It's very likely the base gasket will leak if you don't replace it, because it's hard to remove the head without breaking the seal. Also, if you do all that work and spend the $$$ on a head gasket, only for the base gasket to leak when you put it back together, you will cry yourself to sleep.

Yamanube · « **Reply #39 on:** March 30, 2010, 11:01:45 AM »

Is it bad to put my topend back on without hone/rings? Will I lose compression? Assuming they are in good shape already, that is.

lrutt · « **Reply #40 on:** March 30, 2010, 11:05:05 AM »

Better put a new cam chain in. the old one just saw a lot of stress.

bistromath · « **Reply #41 on:** March 30, 2010, 11:38:26 AM »

Quote from: Yamanube on March 30, 2010, 11:01:45 AM

Is it bad to put my topend back on without hone/rings? Will I lose compression? Assuming they are in good shape already, that is.

If they're in good shape, you won't lose much compression. Rings are expensive, too. But while it's apart, you might want to do it, just to have it done. I know you don't want to do major surgery, but it's better to do things once than have to tear into it again.

Quote from: lrutt on March 30, 2010, 11:05:05 AM

Better put a new cam chain in. the old one just saw a lot of stress.

That's a good point, too, but that's even MORE major surgery, since to do a cam chain right you have to split the cases.

wrenchmuch · « **Reply #42 on:** March 30, 2010, 06:47:24 PM »

Have you determined the reason you lost oil to that side of the head ? If it was a blocked passage you need to clean out your engine or you could end up killing your new parts . You bought the gasket kit so you have what you need to pull it apart and get it back together .

Yamanube · « **Reply #43 on:** March 30, 2010, 07:31:05 PM »

Quote from: wrenchmuch on March 30, 2010, 06:47:24 PM

Have you determined the reason you lost oil to that side of the head ? If it was a blocked passage you need to clean out your engine or you could end up killing your new parts . You bought the gasket kit so you have what you need to pull it apart and get it back together .

I just pulled the head off/apart today. All four of the screws that hold the caps down on those two cylinders where finger tight. I will be checking to see if the oil passages are plugged later this week. The cylinder walls look real nice still but the piston and combustion chamber/valves have quite a bit of scale/carbon build up. I really am leaning towards cleaning out the oil passage (if it is blocked) replacing all the gaskets in the topend and replacing the valve train parts.

bucky katt · « **Reply #44 on:** March 30, 2010, 08:05:08 PM »

Quote from: Yamanube on March 30, 2010, 11:01:45 AM

Is it bad to put my topend back on without hone/rings? Will I lose compression? Assuming they are in good shape already, that is.

just check the cylinders before re-assembly to be sure theres no ridge in the cylinder liners.

lrutt · « **Reply #45 on:** March 31, 2010, 05:50:12 AM »

you don't have to split cases to do cam chain, cut old chain, attach new one to end of old one, pull it through and back up around sprocket on top. re-rivet with rivet tool. Done.

IHWillys · « **Reply #46 on:** March 31, 2010, 07:18:17 AM »

Quote from: wrenchmuch on March 27, 2010, 06:55:44 PM

Unfortunately plugged head passages are a common problem along with lifting cam towers . When the towers lift off the head pressure can be lost to the cam towers . There are cover mods to try and address this .

So are the loose/finger tight caps the culprit or a result?

I read "When the towers lift off the head pressure can be lost to the cam towers" and then read of the loose caps found in this engine. So did the loose caps allow the towers to lift and lose pressure? Or are the loose caps the result of lost pressure?

Ken

bucky katt · « **Reply #47 on:** March 31, 2010, 07:34:01 AM »

Quote from: IHWillys on March 31, 2010, 07:18:17 AM

Quote from: wrenchmuch on March 27, 2010, 06:55:44 PM
Unfortunately plugged head passages are a common problem along with lifting cam towers . When the towers lift off the head pressure can be lost to the cam towers . There are cover mods to try and address this .

So are the loose/finger tight caps the culprit or a result?

I read "When the towers lift off the head pressure can be lost to the cam towers" and then read of the loose caps found in this engine. So did the loose caps allow the towers to lift and lose pressure? Or are the loose caps the result of lost pressure?

Ken

sounds like that could very well be the culprit. make sure, when putting the new cam towers on, that all 4 recesses have o-rings in them, even the 2 recesses that dont have oil holes in them

Yamanube · « **Reply #48 on:** March 31, 2010, 08:09:11 AM »

I will double check the passages to make sure nothing is plugged. My cylinders look pretty good IMO, still can slightly see some hone marks so I think I will just leave the rings/bores alone and cross my fingers that I don't regret it later.
I still have two jetskis to rebuild and assemble so I can't blow all my money on this bike.

bucky katt · « **Reply #49 on:** March 31, 2010, 08:30:26 AM »

yeah, if you can still see the crosshatch on the cylinder walls then your'e ok there. if youre not sure whatr o-rings i'm talking about here is the diagram showing them. theyre only showing 3 of them though there are actually 4 of these tiny o-rings under your cam towers. the number for them on the diagram is 17.

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Author Topic: Motor locked up today. What's next? (Read 5598 times)

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