Topic: Would you want Refurbished Engines?

[HondaMan]

Someone has asked if I'd like a few 750 engines. How much interest might there be in fully-refurbished CB750K1-6 engines?

They would be bored and fitted with new pistons, bronze valve guides and attendant valve seat recuts, new cam chain tensioners and/or chain if needed, and the bottom end gone through with a listing of the bearing clearances and [possibly] pictures of the condition of the C2-C5 gear pair and the shift forks, and the shift drum's grooves. Primary chains and tensioner would be replaced if they exceed Honda's 50% worn guideline. Clutch plate would be replaced if necessary, and the clutch hub modified for improved oiling and cooling per my book. Cases would be repainted where they originally were, but the non-painted side and cam covers would be as-is in most cases, probably showing some wear.

In other words, my typical rebuild...

Is there much interest in buying these outright? I don't plan to do an "engine swap" program, as I don't have the space needed to inventory a bunch of engines. I already have 4 of them, which is 2 past my practical space limit!

Estimated cost would be around $2000 - $2400 which is the average cost of a full refurbishment. I don't do 'overhauls', as those do not include boring to round cylinders or replacment of valve guides: rarely do I NOT change the guides in 750 engines, and then only if they are the Stellite type and in good shape, as those can last 100,000 miles.

[Stev-o]

Hey Hondaman...

Personally, I would not be interested as I've done my own rebuilds [with the help of a buddy in his shop].

But I do see this potentially a good option for some guys who dont want to mess with a rebuild and want to buy a known good engine. 

The other unknown is shipping, how will it get to the destination?  Would you build a crate and ship it freight?  You're in CO, I'm sure it would cost $200-400 depending on location within the U.S.

Or, the customer does a road trip with their bike [trailered] and it gets installed in your shop?!

[newday777]

Well that would get my 76 on the road this year....... Hmmmmm.
How much to ship to NH?

[Whaleman]

You would almost need to build a custom engine crate attached to a pallet that would be returned. Dan

[Just John]

I know a Honda dealer who did this in the late 90s.  Engines were shipped on a pallet or the customer could deliver/pickup.  When he returned the engine it was wrapped in aviation shrink wrap.

[HondaMan]

Packing is definitely key. I have a crate design that I've been using for 10 years. If the owners build it correctly and strap the engine down, it works well. It is 24" square and 29" tall, so it takes minimal floor space to ship and can go LTL. I've had the best handling and scheduling from R&L Carriers, who hire only Vets for their drivers. Those guys have been TOPS to work with, never damaged anything. Others, not so much. I have received engines in "totalled" condition from some of the other carriers, sad to say. R&L is cost-competitive, usually among the 3 lowest bids.

[HondaMan]

Well that would get my 76 on the road this year....... Hmmmmm.
How much to ship to NH?

It would be in good company: I have 3 other 750s running around in NH already.

You can get a quote easily from places like Uship.com or Freightcenter.com (avoid UPS and Fedex for this, they broke every engine I ever shipped thru them).
My shipping ZIP is 80232, Residential Delivery. This costs $35-$50 extra, as I don't have a pickup truck to go get/send them at a terminus, which is 90 minutes' drive from here, anyway!

The crate weight is about 225 lbs, usually. If you under-estimate the weight there is often a penalty (about $25-$45, depending on how much error) and the charge for the extra weight. They sometimes refund if you overestimate, but not always! This crate is usually underweight about 5-8 lbs, unless someone uses sides of 1/2" plywood, or something like that: I use floor underlayment (3/16") and mark "DO NOT STACK" on the tops.
 

[MRieck]

 I would not recommend using bronze guides as they aren't durable. I have personally seen this multiple times. The valve angle and increased side load produced by a rocker arm valve train ( as opposed to a shim/bucket arrangement) can wear out bronze guides in 5,000 miles.
I'd use the Kibblewhite iron guides that CycleX sells......I use them almost exclusively. 

[jamesw]

I think there's a market for your engines Mark.

I would have bought one had the CDN dollar have been stronger when I was building my bike.

[DickL]

Having used Mark's services twice...i would recommend his engines without reservation.  Transport cost about 250 from R&L from Denver to Massachusetts. His pricing is modest. My most recent Hondaman engine is an 836 due to a cleamup which is in matching number 1970K0.  Wholeheartedly I reccomend his engines and his services!

Dick Listro

[MauiK3]

Mark did the head and cylinders for my K3, outstanding work.
Shipping to and from Maui was painful but I was determined to get these right.
The entire engine would likely be better than stock.

Mark, how would you handle the primary cushion? That was a decision point for me.

[PeWe]

I would not recommend using bronze guides as they aren't durable. I have personally seen this multiple times. The valve angle and increased side load produced by a rocker arm valve train ( as opposed to a shim/bucket arrangement) can wear out bronze guides in 5,000 miles.
I'd use the Kibblewhite iron guides that CycleX sells......I use them almost exclusively. 

My K6 head with 5mm valve stem kit had bronze guides. Really worn after 25.000 km. The upper ends were really wide.

That head got CycleX cast iron guides cryo treated for a few bucks more. Good oversize for a head that got its 4th set of guides.

And their stainless valves, 34/28mm, stock sized stems.
I could not miss the opportunity to buy 34mm inlet valves for my K head that have seats ported for it.

Their std guides cost less than Honda stock guides.

[DickL]

Bump

[HondaMan]

We started using the APE bronze valve guides because with no top-end lube in gasolines today (i.e., unleaded gas) and additional solvents like ethanol being added. The stock Honda cast iron guides dissolve into an oval at top & bottom ends very quickly, like in 5000 miles. Virtually 100% of the heads I've seen since the 1990s have suffered this problem, usually to the point of weeping oil.

The bronze guides, on the other hand, MUST be installed with smaller clearances. I usually set the stem clearances at 80% of the minimums used for cast-iron guides (like Honda's OEM parts) for cooler runnig and mighty long life. I haven't seen nor heard much of wear in bronze guides done this way: my first use of them was in the Ford 390 CID engines where we bored the cast iron guides that tyically wore out at 70k-80k miles to the point of sucking oil, and installed bronze liners, sizing them by forcing a precision-sized hard steel ball thru them. When I tried this in the 750 Honda guides it just cracked them for not being supported enough (Ford's are in a cast-iron head, not aluminum). These lasted well over 100,000 miles in the 390 engine (before I sold the car, heard last week they are still in it 12 years after that) and more than 350,000 miles in my I6 Ford engine without burning a drop of oil in 4000 mile change schedules.

We bore the APE bronze guides at between 8K-10k RPM, slowly (which is why the sizing cost is high) so they come out polished. Having worked in a machine shop of one type or another since 1991, this has always been the best (if expensive) way to cut and polish bores of any type, especially those of less than 0.0004" (4 tenths) hole-to-shaft clearances. If they get bored conventionally and then polished or honed to a tight clearance it doesn't work as well in the end because the polishing activity is not as controllable (to make it straight). So, I apply this method to these engines, too.

I have only ever built one engine using the Dynoman valve guides, and never heard back anything about the bike in the end, so I can't speak for those. They offer some oversized OD guides, which was the reason they were used: someone had done a poor job of replacing the guides with some new cast-iron ones, cracking one in the process, which was how I ended up with that particular head. That machine shop had honed the guide holes before installing the new guides, and I tapped them out with a tiny hammer and a wooden dowel, they were that loose. The owner sent me the cylinders next, as they had been bored to more than 0.0020" piston clearance for some step-size cast pistons, and he knew that wasn't right, either. That poor guy paid twice for his rebuild.

[Jimcg]

We started using the APE bronze valve guides because with no top-end lube in gasolines today (i.e., unleaded gas) and additional solvents like ethanol being added. the stock Honda cast iron guides dissolve into an oval at top & bottom ends very quickly, like in 5000 miles. Virtually 100% of the heads I've seen since the 1990s have suffered this problem, usually to the point of weeping oil.

Always very interesting to read the things you and other knowledgeable members share. The part I quoted raises a question inside: Would you recommended using lead substitute with today's gas? I'm running a '82 CB650. I do that in my '55 Chevrolet.

/Jim

[newday777]

Mark
Do you run the motors before you send them out?
Do you have a K6 motor?

[HondaMan]

We started using the APE bronze valve guides because with no top-end lube in gasolines today (i.e., unleaded gas) and additional solvents like ethanol being added. the stock Honda cast iron guides dissolve into an oval at top & bottom ends very quickly, like in 5000 miles. Virtually 100% of the heads I've seen since the 1990s have suffered this problem, usually to the point of weeping oil.

Always very interesting to read the things you and other knowledgeable members share. The part I quoted raises a question inside: Would you recommended using lead substitute with today's gas? I'm running a '82 CB650. I do that in my '55 Chevrolet.

/Jim

I usually recommend (FWIW) using an ounce of oil in the tank of gas at fillup. I used to add the old "top Oil" that you could buy in little bottle, perfect for carrying in my fairing. Those went away for some reason. So, I switched to 2-stroke oil, either regular or synthetic (whatever is available). The oil does several things: first, it helps with top-end lube when there is none in the gas (100% of today's fuels), it smoothes out the carb operation (mechanically) with a bit of lube, and it prevent tank rust, which is REAL important when our modern gas with ethanol can absorb lots of moisture from the air into the ethanol. The water gets pushed off the metallic surfaces by this small amount of oil, so the surfaces benefit.

[HondaMan]

Mark
Do you run the motors before you send them out?
Do you have a K6 motor?

I can, if the owner wants it. I run them for 15 minutes and set the ignition timing so they are drop-in ready, and it helps check for any oil leaks that might happen. Once I got one with a hairline crack in the oil filter housing, totally invisible, around the oil filter's bolt. Someone had overtightened it big-time, probably because of the too-thin O-rings that come in the oil filter "kits" these days - BTW: those fit Kawis and Suzukis after 1985, but not these Hondas - and as soon as it pressured up, there was a pool of oil all over my garage floor.

Yeah...

Not just once, but twice, as I couldn't see the crack!

Yeah, yeah...

So it also got a new, used oil filter housing in that one's rebuild.

The K6 can used any engine K4-K6, as a drop-in replacement. The K1-K3 have a different size of oil tank breather port on the back of the engine, so while they will also fit, you must go to an auto parts store and get one of the little Dorman Parts' adapters that step the 2 different hose sizes together that your oil tank might have different from the engine. I have also seen K6 engines come with both size ports back there (and with oddball pistons and cams) because the K6 was a Honda scramble to re-make the K5 after it was discontinued, but sales of the F0 fell flat (40% of expectations). Honda hurriedly found any K5/F0 parts they could make into the 'new' K6 that showed up mid-year in 1976 (March-ish) so it can have, alternately:
1. an F0 engine with exhaust spigots on th ehead to fit the 4 pipes,
2. a K5 bottom end with F0 top end,
3. an F0 bottom end with K5 top end,
4. either bottom end with a K5 head and F0 pistons (these are hotrods with 9.5:1 compression ratio)
5. either bottom end with K5 pistons and F0 head (they are doggy with 8.8:1 compression ratio)
6. either 657b, 7a, or 086a/b carbs. This means the choke lever can even hit the fuel petcock with one combination of these.

So, when replacing a "K6 engine" with another, I tend to think of a K4/5 engine as the new one, just to make sure it will drop in!

You're the 2nd one to ask about a whole engine, so I think I'll talk with this fellow rider about obtaining these engines. It will give me a winter project, making some ready-to-ship engines!

[Jimcg]

I usually recommend (FWIW) using an ounce of oil in the tank of gas at fillup. I used to add the old "top Oil" that you could buy in little bottle, perfect for carrying in my fairing. Those went away for some reason. So, I switched to 2-stroke oil, either regular or synthetic (whatever is available). The oil does several things: first, it helps with top-end lube when there is none in the gas (100% of today's fuels), it smoothes out the carb operation (mechanically) with a bit of lube, and it prevent tank rust, which is REAL important when our modern gas with ethanol can absorb lots of moisture from the air into the ethanol. The water gets pushed off the metallic surfaces by this small amount of oil, so the surfaces benefit.

Your recommendation is worth a lot. Many thanks! 2 stroke oil is an easy thing to add and especially if doing so can reduce risk of engine problems.

/Jim

[ekpent]

 Did not know a K6 engine could be such a mutt ! 

[HondaMan]

Did not know a K6 engine could be such a mutt ! 

I find them most interesting because of their mix. They ranged between 'doggy' ones, 'regular' ones, and the rare 'hotrod' ones, but all looked alike. It was those engines that taught me about the mainshaft shims, the internal gearing differences between "K" and "F" (and some of the K6 do have the "F" lower primary drive) types, and the frustrations of having the petcock and choke end up on the same side of the tank. These are the bikes that most often suffer slow-fuel problems, like when they have the lower primary drive ratio with the lower-compression pistons, the "F" head, and one fuel outlet. At redline speeds on a dragstrip they can emtpy the float bowls faster than the tank can fill them, as one example.

This is also the core of the famous hi-MPG engine: "F" pistons under the "K" head with the "K" primary drive ratio and the 086a carbs with one-outlet petcock. Those bikes could reach 50 MPG regularly at 55 MPH touring speeds, yet would run on Regular (1970s) grade gas without trouble. Their top speed was low, at usually around 95-100 MPH, but no one noticed that back when.

The K6 wiring harness could be confusing, too: I have seen those queries pop up here from time to time when the wiring diagrams don't show things like jumper wires that are male on both ends with [a color] and [a color band] on one end. This happens when part of the wiring harness came from the F0 (body) and part from the K5 (handlebars), which ended up with the wrong number of male plugs in the headlight.

[MRieck]

We started using the APE bronze valve guides because with no top-end lube in gasolines today (i.e., unleaded gas) and additional solvents like ethanol being added. the stock Honda cast iron guides dissolve into an oval at top & bottom ends very quickly, like in 5000 miles. Virtually 100% of the heads I've seen since the 1990s have suffered this problem, usually to the point of weeping oil.

The bronze guides, on the other hand, MUST be installed with smaller clearances. I usually set the stem clearances at 80% of the minimums used for cast-iron guides (like Honda's OEM parts) for cooler runnig and mighty long life. I haven't seen nor heard much of wear in bronze guides done this way: my first use of them was in the Ford 390 CID engines where we bored the cast iron guides that tyically wore out at 70k-80k miles to the point of sucking oil, and installed bronze liners, sizing them by forcing a precision-sized hard steel ball thru them. When I tried this in the 750 Honda guides it just cracked them for not being supported enough (Ford's are in a cast-iron head, not aluminum). These lasted well over 100,000 miles in the 390 engine (before I sold the car, heard last week they are still in it 12 years after that) and more than 350,000 miles in my I6 Ford engine without burning a drop of oil in 4000 mile change schedules.

We bore the APE bronze guides at between 8K-10k RPM, slowly (which is why the sizing cost is high) so they come out polished. Having worked in a machine shop of one type or another since 1991, this has always been the best (if expensive) way to cut and polish bores of any type, especially those of less than 0.0004" (4 tenths) hole-to-shaft clearances. If they get bored conventionally and then polished or honed to a tight clearance it doesn't work as well in the end because the polishing activity is not as controllable (to make it straight). So, I apply this method to these engines, too.

I have only ever built one engine using the Dynoman valve guides, and never heard back anything about the bike in the end, so I can't speak for those. They offer some oversized OD guides, which was the reason they were used: someone had done a poor job of replacing the guides with some new cast-iron ones, cracking one in the process, which was how I ended up with that particular head. That machine shop had honed the guide holes before installing the new guides, and I tapped them out with a tiny hammer and a wooden dowel, they were that loose. The owner sent me the cylinders next, as they had been bored to more than 0.0020" piston clearance for some step-size cast pistons, and he knew that wasn't right, either. That poor guy paid twice for his rebuild.

 Don't want to be $hit stirring but I saw this on Mike Nixon's website. He has other things to say about SOHC 750 internet advice.
"Incredible! First, the factory cast iron valve guides are the longest wearing of any you could possibly use, and measurably, hugely, longer-wearing than any bronze guides. Unbelievable. Second, lead in the fuel has as much to do with this issue as the man on the moon. No vintage Honda four-cylinder was ever manufactured that needed or benefitted from tetra-ethel lead. "Oil in the gas"? No. There are at least five solid reasons to never do such a thing, not to mention that it is entirely unnecessary. Absolutely incredible. Far from an isolated example, this is what you subject yourself to when you believe the things forums tell you. "

[754]

At the end of the day, you keep doing what works for you.
Sometimes its not just the parts, how they are setup changes things.. there are variables..

[Don R]

 I'll continue to use a little 2 stroke oil in my gas because I love my wrinkle tanks and my 4-4 exhausts, a little carb lube can't hurt either.

[HondaMan]

I find it interesting the things the internet can come up with, especially when they contradict long time (since 1975), real-life experiences.
Cast-iron valve guides in these engines are the #1 wear item in the K3/4/5/6 and F1/2/3, K7 and K8 engines, much sooner than the rings. The K0/1/2 and the F0 engines received Stellite guides, which are a special cast-iron alloy with hardened fillers, and these have a blue hue to them when compared with the other, normal cast iron guides. These are hard as glass (and can chip like it on the tips of the pointed, seal-less guides of the K0/1 engines) and can last over 100,000 miles (and many do, even my own went 131k miles and were just reaching tolerance). But, chances are that if you pick up any of the non-Stellite heads referenced here, you will find the guides are worn to oil-leaking status by 15k miles or so. This begins when the intake valve can wiggle in-out toward the center of the chamber by 0.0032" when lifted 0.25" off its seat and the exhaust 0.0060" in the same fashion. The latter will pump oil out the exhaust port, making a mess of the front of the engine. The guides wear most at the top where the rockers side-load them, and the fulcrum action of the center portion of the guide wears the head-side of the guide at the opposite side, toward the ports.

I have built/rebuilt by now hundreds of the SOHC4 engines. This has been consistent in all of them.