Topic: oily plugs again, could it be valve seals?

[bluesoverlord]

Yes, there are 4 o-rings under the tower as IW said. The PO forgot them and it makes sense that your outside cam bearings were put at risk by him. Ken at Cycle-X knows what he is talking about from everything that he has told me. I'm also going with the MLS head gasket that he suggested.

[markreimer]

Yes, there are 4 o-rings under the tower as IW said. The PO forgot them and it makes sense that your outside cam bearings were put at risk by him. Ken at Cycle-X knows what he is talking about from everything that he has told me. I'm also going with the MLS head gasket that he suggested.

Sounds good. I ordered 4 replacement o-rings and will fit them on both sides. Thanks!

[markreimer]

The diameter of the valve heads will be different, intake is 32 mm I think, and exhaust is 28 mm (stock sizes). That being said, the diameter of the valve stems is exactly the same for the intake and exhaust valves.

I've also heard nothing but good things about Competition Engine!

Glad to hear you've heard good things as well. Makes me feel good.

Are you sure about the diameter? You are referring to the actual valves themselves, not the valve guides right? That I am aware of - I noticed the different sized valves when I was taking them out of the guides/head.

My confusion is around the valve guides only, as I received a package of 8 valve guides that seem to be the same. I had thought the intake and exhaust guides were different. Perhaps not?

I did some more poking around and have found a number of guide kits that seem to have 8 identical guides. Cycle-X looks the same way.

[jneuf]

The diameter of the valve heads will be different, intake is 32 mm I think, and exhaust is 28 mm (stock sizes). That being said, the diameter of the valve stems is exactly the same for the intake and exhaust valves.

I've also heard nothing but good things about Competition Engine!

Glad to hear you've heard good things as well. Makes me feel good.

Are you sure about the diameter? You are referring to the actual valves themselves, not the valve guides right? That I am aware of - I noticed the different sized valves when I was taking them out of the guides/head.

My confusion is around the valve guides only, as I received a package of 8 valve guides that seem to be the same. I had thought the intake and exhaust guides were different. Perhaps not?

I did some more poking around and have found a number of guide kits that seem to have 8 identical guides. Cycle-X looks the same way.

Oops! Sorry, misread your post...I thought you meant the valves.

I may be wrong, but I'm pretty sure the guides are the same. Hopefully someone can come and confirm.

You've got me wanting to shovel a path to my garage now so I can get to my bike!

[MRieck]

The diameter of the valve heads will be different, intake is 32 mm I think, and exhaust is 28 mm (stock sizes). That being said, the diameter of the valve stems is exactly the same for the intake and exhaust valves.

I've also heard nothing but good things about Competition Engine!

Glad to hear you've heard good things as well. Makes me feel good.

Are you sure about the diameter? You are referring to the actual valves themselves, not the valve guides right? That I am aware of - I noticed the different sized valves when I was taking them out of the guides/head.

My confusion is around the valve guides only, as I received a package of 8 valve guides that seem to be the same. I had thought the intake and exhaust guides were different. Perhaps not?

I did some more poking around and have found a number of guide kits that seem to have 8 identical guides. Cycle-X looks the same way.

Don't worry about it. The OEM exhaust guides are a little longer than the intakes but it makes no difference. Less guide sticking in the exhaust port.

[Duanob]

It occured to me you never mentioned which spark plugs you're running? Maybe I missed it. If you're running the wrong plugs and they are on the cold side this will easily cause carbon build up and foul plugs.

I just posted this in another thread about plugs:

http://www.ngksparkplugs.com/tech_support/spark_plugs/p2.asp

[markreimer]

It occured to me you never mentioned which spark plugs you're running? Maybe I missed it. If you're running the wrong plugs and they are on the cold side this will easily cause carbon build up and foul plugs.

I just posted this in another thread about plugs:

http://www.ngksparkplugs.com/tech_support/spark_plugs/p2.asp

Hi Duanob - I'm running what I understand are stock -  D8EA plugs I believe. Whatever the manual states, and ordered through my local Honda dealer. I have the good fortune of dealing with a guy there who has a cb400F and loves these old bikes.

Here is the latest progress on the bike. I've made some big headway, and had a few setbacks.

I got the head back from Competition. They soda blasted it and boy was it CLEAN!! I had new APE guides put in and honed. The valves were fine, just cleaned up. I had the seats cut and then I lapped the valves in on my apartment kitchen table. I have an understanding woman 

I cleaned the pistons with a brass wheel for the big carbon chunks, then scrubbed the whole surface with a scotchbrite pad and mineral spirits. It cleanup very well, but took some elbow grease. I had started with a gasket scraper, but it seemed to want to gouge the surface so I opted for something slow and steady and safe.

I oiled the valve stems, and the cylinder walls lightly before rebuilding. I used hondabond under the rubber pucks. Blue loctite on the cam tower bolts. Everything was torqued and re-torqued according to manual specs. I used new valve seals, new head gasket, replaced the oil pump screen, new cam cover gasket.

Oh, and also whoever recommended taping those little oil orifices in the head, THANK YOU! I had a close call with them falling out when I took it to the shop. One of them was very dirty and probably totally blocked. I cleaned them out completely, and blew compressed air through all the oil passages in the head and the block.

Got the engine back in and spent about 20 minutes priming the oil pump before I saw oil flowing into the filter house, main galley, and finally up to the top end. No sense in frying a rebuilt engine!

So far everything was working great - I had the whole bike back together, I was getting oil everywhere it needed to be, time to fire it up.

I didn't have new plugs on me, just the old fouled plugs that wouldn't fire before - the reason I started this whole project to begin with. I cleaned them as best I could with alcohol and scotchbrite.

Moment of truth - I hit the starter and it fires up immediately. It sounded a bit sluggish, similar to how it did before when not all the cylinders were firing. I thought maybe I hadn't cleaned the plugs well enough, or its just from sitting for 6 months and being rebuilt. I give it a bit of gas... starting to smooth out. A bit more gas... BANG!!!!!! It sounded like a gun was fired in my ear. I hit the kill switch and saw a bit of blackish smoke coming out of hte right pipe. $%@$ I killed my bike in 20 seconds.

Or did I... That makes no sense. Everything was put back correctly I'm sure. I had two other guys look it over while building it. It hadn't been running long enough to overheat if there was an oil issue. Then I noticed something sticking out of the snowbank a few meters from the shop garage door that was open. I blew the baffle clean out of my right pipe! The weld had broken last year already, and the baffle was stuck in from friction ever since. I guess it had enough. 

I tried turning the engine over with the kick starter - there was no unusual resistance, weird noises or things out of the ordinary. If I blew up my motor, I figured I'd notice something. So I tried firing it up again. It started up right away again, only this time the right side sounds like a demon out of hell roaring for all it's worth, and the left side is normal and quite haha. Well hey... At least it runs. I guess it's time to sort out an exhuast option now...

[flybox1]

IIRC,  D8ES-L was stock, and was replaced with the D8EA
Denso X24ES-U's are now closest to the correct heat range for CB750's

[Duanob]

According to the NGK website you might try dropping down to a 7 plug (or Nippon denso equivilant). It will burn hotter to help keep the carbon from building up. Since you need new plugs anyway its worth a try.

Remember the D8s were stock for the 1970s. gas today has changed and is full of detergents and crap that todays hotter ignition systems don't have too much trouble burning off but your old system will build up carbon. I had trouble with build up after just a couple of months. I had the head rebuilt and had everything was clean. The head gasket was bad and I had to go back in and replace it. When I went in again all the pistons and valves had a lot of carbon build up and had to be cleaned again. If you do mostly city driving you should be using a hotter plug to help burn off this carbon.

[markreimer]

According to the NGK website you might try dropping down to a 7 plug (or Nippon denso equivilant). It will burn hotter to help keep the carbon from building up. Since you need new plugs anyway its worth a try.

Remember the D8s were stock for the 1970s. gas today has changed and is full of detergents and crap that todays hotter ignition systems don't have too much trouble burning off but your old system will build up carbon. I had trouble with build up after just a couple of months. I had the head rebuilt and had everything was clean. The head gasket was bad and I had to go back in and replace it. When I went in again all the pistons and valves had a lot of carbon build up and had to be cleaned again. If you do mostly city driving you should be using a hotter plug to help burn off this carbon.

Thanks! I'll order some up today

[iron_worker]

A hotter plug will only help burn off deposits from the plug itself. It won't change how the deposits build up on the piston or head.

Also, going to a hotter plug to burn off oil deposits (or even carbon deposits) can in a lot of cases be a bandaid masking the symptoms of a bike that is burning oil or is excessively rich.

If you are running a stock plug and getting a lot of building up inside the combustion chamber I would first look at if you're burning oil or running rich before ever suspecting the plug. Tuning the plug heat range is a fine detail that should be sorted out after your AF is tuned and bike is running properly/not leaking or burning oil.

Of course, that's just my $.02. 

IW

[markreimer]

A hotter plug will only help burn off deposits from the plug itself. It won't change how the deposits build up on the piston or head.

Also, going to a hotter plug to burn off oil deposits (or even carbon deposits) can in a lot of cases be a bandaid masking the symptoms of a bike that is burning oil or is excessively rich.

If you are running a stock plug and getting a lot of building up inside the combustion chamber I would first look at if you're burning oil or running rich before ever suspecting the plug. Tuning the plug heat range is a fine detail that should be sorted out after your AF is tuned and bike is running properly/not leaking or burning oil.

Of course, that's just my $.02. 

IW

Yes, agreed. I tore the bike apart because the plugs were always wet with oil - my valve guides were worn out and the seals were rock hard. I have new guides installed, seals, valve seats re-cut and lapped in.

I don't know if my carbs are tuned perfectly yet, but I suspect not. It runs well and doesn't have any flat spots that I can perceive, but my plugs were consistently blacker than they should be.

My next steps are:
1 - buy new plugs - going to try the Denso X24ES-U
2 - fix the baffles in my exhaust
3 - Ride around for a couple days and make sure I don't have leaks
4 - plug chop and tune the carbs accordingly
5 - riderideriderideride

[HondaMan]

Hi guys,

Here's the latest update on the head.

I just received my valve guides from 4into1.com

I bought this set of 8 valves:  http://4into1.com/ape-high-performance-bronze-valve-guides-honda-cb750/

I realized while looking at them that they seem to be the same 8 valves. Aren't the exhaust and intake valves different sizes? Did I just waste a bunch of money buying double the valves I need?? All the listings for this product on all the sites I've visited say that this package is good to redo all the valves in the head. I'm confused!

Yes, the exhaust valves are smaller than the intakes. (Uh-oh?) 
There is also blowby showing on the piston (your picture of #3 above). That 'clean' spot on the top of the piston indicates the gases are slipping past the rings there, which cleans the carbon off around the edges of the crown. Often, folks do not hone the cylinders NEARLY enough when they replace rings: you must hone them until all traces of the old shiny sides are gone. The normal method here is to hone them until they reach this state, then measure the piston skirt-to-bore clearance with feeler gages. If the clearance is more than spec (0.025" is my 'max'), it is time for a rebore with bigger pistons. Even a 0.25mm overbore (0.010") will restore a lot of lost power, because the now egg-shaped bores will then become round again. After that, they will stay round for a LONG, LONG time because the sleeves are now 'cured' from use. Typically this yields about +10% in HP and torque over your starting point.

Those guide clearance numbers sure indicated that the guides were done, and even new seals would not hold back the vacuum enough to keep the oil where it belonged. The K4 usually delivers about 25k miles with their cast iron guides, and the bronze ones are an excellent step up in performance and longevity. They have about 1/2 the friction of the old iron ones.

The O-rings around the oil jets and the "other end" of the cam towers are VITAL. The stock size was called out as 1.9 x 5.9mm, but a 2x6mm will fit fine and is easier to find. If yours were missing on the outer ends of the cam bearings, that is the reason for the loss of the bearings at the outer ends, for sure. Usually it causes the inner ones to be destroyed as well, so maybe you just didn't have enough miles on it that way, yet? Loss of those O-rings drops the top end oil flow to about 25% of normal (because it all leaks away), which tears things up pretty fast.

[markreimer]

Hi guys,

Here's the latest update on the head.

I just received my valve guides from 4into1.com

I bought this set of 8 valves:  http://4into1.com/ape-high-performance-bronze-valve-guides-honda-cb750/

I realized while looking at them that they seem to be the same 8 valves. Aren't the exhaust and intake valves different sizes? Did I just waste a bunch of money buying double the valves I need?? All the listings for this product on all the sites I've visited say that this package is good to redo all the valves in the head. I'm confused!

Yes, the exhaust valves are smaller than the intakes. (Uh-oh?) 
There is also blowby showing on the piston (your picture of #3 above). That 'clean' spot on the top of the piston indicates the gases are slipping past the rings there, which cleans the carbon off around the edges of the crown. Often, folks do not hone the cylinders NEARLY enough when they replace rings: you must hone them until all traces of the old shiny sides are gone. The normal method here is to hone them until they reach this state, then measure the piston skirt-to-bore clearance with feeler gages. If the clearance is more than spec (0.025" is my 'max'), it is time for a rebore with bigger pistons. Even a 0.25mm overbore (0.010") will restore a lot of lost power, because the now egg-shaped bores will then become round again. After that, they will stay round for a LONG, LONG time because the sleeves are now 'cured' from use. Typically this yields about +10% in HP and torque over your starting point.

Those guide clearance numbers sure indicated that the guides were done, and even new seals would not hold back the vacuum enough to keep the oil where it belonged. The K4 usually delivers about 25k miles with their cast iron guides, and the bronze ones are an excellent step up in performance and longevity. They have about 1/2 the friction of the old iron ones.

The O-rings around the oil jets and the "other end" of the cam towers are VITAL. The stock size was called out as 1.9 x 5.9mm, but a 2x6mm will fit fine and is easier to find. If yours were missing on the outer ends of the cam bearings, that is the reason for the loss of the bearings at the outer ends, for sure. Usually it causes the inner ones to be destroyed as well, so maybe you just didn't have enough miles on it that way, yet? Loss of those O-rings drops the top end oil flow to about 25% of normal (because it all leaks away), which tears things up pretty fast.

Hondaman, can you explain a bit more how you identify blow-by? When I took head off there was an even layer of crusty carbon build-up, maybe 3mm thick or so. Are you diagnosing this based on how the pistons looked after I cleaned them up?

Regarding the guides, hmm. Not sure what to say about it honestly, other than that I gave the guides to a reputable motorcycle engine shop and they put them in without an issue. You say they are smaller? As in shorter, or less diameter? I presume it must be length because all 8 were pressed in tight. What would be the repercussion of using incorrect guides?

Thanks for weighing in on the o-rings as well. The inner bearing journals on the towers were in great shape. It was really the outer journal above #4 that was in bad shape.

Going to attempt to fix the baffling tomorrow and fire it up again.

[HondaMan]

Also forgot to attach this. I believe this is cylinder #3. It looks like scratches on the cylinder walls. I did a compression test at the beginning of last season and had great even numbers across all four. As I mentioned before, the PO put new rings in just before I bought the bike. Any ideas what would cause these marks? Is it something to worry about even?

It was this picture that got me talking about the blowby issue on the rings. The one side of the piston top looks to be swept clean, which often indicates the rings are not sealing on that side.

My comments about the "valve wiggle" measurements you made were directed at your old guides (I think?). You were measuring them the right way. They should not be more than .0032" when lifted about 7mm above the seat, in Honda's usual spec. New guides are supposed to be honed to .0010" to .0012" "wiggle" distance.

Sorry if I caused confusion? What was odd: when I posted the above, there were only 2 pages of posts showing (on my computer, anyway...), yet it shows up well down the 3rd page. Weird? My computer here is mighty old, so it may not be the forum's doing...?

[markreimer]

Also forgot to attach this. I believe this is cylinder #3. It looks like scratches on the cylinder walls. I did a compression test at the beginning of last season and had great even numbers across all four. As I mentioned before, the PO put new rings in just before I bought the bike. Any ideas what would cause these marks? Is it something to worry about even?

It was this picture that got me talking about the blowby issue on the rings. The one side of the piston top looks to be swept clean, which often indicates the rings are not sealing on that side.

My comments about the "valve wiggle" measurements you made were directed at your old guides (I think?). You were measuring them the right way. They should not be more than .0032" when lifted about 7mm above the seat, in Honda's usual spec. New guides are supposed to be honed to .0010" to .0012" "wiggle" distance.

Sorry if I caused confusion? What was odd: when I posted the above, there were only 2 pages of posts showing (on my computer, anyway...), yet it shows up well down the 3rd page. Weird? My computer here is mighty old, so it may not be the forum's doing...?

Hondaman, would a compression test indicate if the rings weren't sealing properly? I did one last summer and had good results. I guess it could have worn out since then.

In other news, I fired it up last night! The baffle had blown out of the right pipe, so I pulled the other out as well to balance the back pressure. I'll be repacking them and installing again, but for now, have a look at how mean it sounds

http://youtu.be/biQV2kC4YCU

Not sure how to embed...

[iron_worker]

Oy! She sounds good.

Have you been for a good ride yet? Report?

IW

[markreimer]

Oy! She sounds good.

Have you been for a good ride yet? Report?

IW

No yet sadly. It's hard to see in the video, but I'm actually snowed in! It snowed about 5cm two days ago and has been sitting around freezing temperature since. The bike is SO loud without baffles that I would surely be pulled over as well. Hopefully this weekend I can take it out with the baffles in.

[markreimer]

It's been nice weather out finally and I've been riding the bike nearly every day for the last week. Good news and bad news.

Good news is that there are no leaks anywhere and oil is flowing to all the places it needs to.

Bad news: I started getting some backfiring after riding the bike for about 15 minutes in the city. It was coming out of the left-side muffler, cylinder 1/2. I double checked the exhaust seal, carb boots, both were on tight and didn't show signs of leaking.

Turns out the plug wasn't firing consistently. I checked the plug wire and it was in kinda bad shape, so I trimmed about 5mm off. The backfiring has almost gone away, but cylinder 2 isn't firing consistently. I pulled the plugs and #2 was quite wet. If I clean up the plug, the bike runs great. Leave it overnight, and sometimes it's wet again.

The carbs were cleaned recently and I checked for stuck floats when I first started getting backfiring. The bowls were shiny and free of sediment, the floats moved freely, and the needle valves were clean and not sticking. I don't think it's a carb issue, but I got new slow and main jets in the mail yesterday since it's running rich, so I'll try replacing them and see if that makes any difference.

Any other ideas of what to look for? Cylinders not firing at start-up was my original problem last year, so redoing the head doesn't seem to have solved that problem.

I checked all four plugs for spark - all have good strong spark when the plugs are new.

The plug does not seem to be wet with oil - it's a much thinner and clear looking wet. If it isn't a carb issue, how else could that be happening?