How To Adjust Valve Lash (1980 Honda CB650 SOHC)

Here I’ve already removed the tank and all of the necessary engine covers.

Since I have already put enough miles on this bike since I got it running to warrant an oil change I decided to re-check the valve adjustment for two reasons; one is that as long as the engine had been sitting without running I want to keep a close eye on it for a while & two so that I could show everyone how I do it. As you can see in the photo above I’ve already removed the gas tank, all four spark plugs  and all of the appropriate engine covers. The first thing to do before you adjust the valve lash is to adjust the cam chain tensioner. On a 1980 Honda CB650 this is done by loosening the nut on the rear of the cylinder just a little bit. Do not remove it just loosen it some

This is the nut you loosen to adjust the cam chain tensioner.

Then put the correct size wrench on the hex spacer behind the nut at the ignition unit on the right side of the engine. Then rotate the wrench clockwise slowly 4 to 5 turns as you simultaneously tighten the lock nut that you loosened at the beginning of this step. This is also the first thing you should try if you own a motorcycle and you can hear the cam chain rattling, but if after making the correct adjustments you still have a rattle then it will be time to start replacing parts. Keep the wrench that you used to turn the crankshaft handy, you are gonna need it a few more times.

The Clymer manual describes this as a 15/16″ nut. That is wrong this is a 24mm. OOPS

Here in this picture taken on the left side of the engine you can see 2 of the three openings in which we will be working to check & set the valve lash. The adjusters for the intake valves are on the back of the head in front of the carburetors and the exhaust valve adjusters are on the front of the head behind where the exhaust pipes stick out. The first step is to get the number 1 cylinder to top dead center. Take your large wrench and rotate the crankshaft clockwise and watch for the intake rocker arm on the first cylinder to drop down into the head and start to rise back up. Then look at the timing marks on the ignition advance unit (photo is further down the page) and continue to slowly turn the engine until the 1.4 T mark is aligned with the pointer that is cast into the crankcase.

The camshaft & rocker arms are in the left hole & one of the adjusters is in the right hole.

At this point both the intake & exhaust valve on cylinder number one should be loose enough both rocker arms to be wiggled. If not you either have a valve that is way too tight or you did not stop turning the crankshaft at the right mark, either way you should verify which problem you have before moving on. a simple way to see if the cylinder is at top dead center is to take a long small diameter wooden or plastic dowel and insert it into the spark plug hole. If the piston is at the top of the cylinder the dowel will not go in very far at all.

With the number one piston at TDC on a 1980 CB650 you should be able to adjust both valves on the number one cylinder, The exhaust valve on number two, & the intake valve on number three. Once you have those done you need to repeat the step above but this time watch the intake rocker of cylinder 4 on the right side of the motor cycle. With that one at TDC you can adjust both valves on number four, the exhaust valve on number three, and the intake valve of number two.

Lets talk about tools for a little bit. All of the shop manuals show a special tool for adjusting the valves, but the simple truth of the matter is that for a number of engines you don’t need them and this CB650 is one such example. For the lock nut, I just clamped a pair of Vise Grips around an old cheap 10mm socket that I have on hand and then just used the proper size of flat-head screwdriver to turn the adjustment screw with. Works great for me on this motorcycle, your mileage may vary, if you break something I’m not responsible, etc.

Macgyver was an amateur!

Speaking of tools let’s get the feeler gauges to set the valves with. The ones that I use are from Snapon and are about a foot long. The also came with a nifty holder that is very handy for working with the really thinner sizes in hard to reach places. The intake valve lash setting for this generation of Honda CB650 is .05mm (.002 inches) and the exhaust setting is .076mm (.003). So to do this job I will get out three feeler gauges in sizes .002,.003 & .004 (.1mm). Why three sizes? I’ll explain in a minute.

The next picture is of the .002 feeler gauge slipped in between the rocker arm & camshaft. This is where you measure the lash on this engine. Basically what I do is turn the adjustment screw until I can just slip the feeler gauge into place with just a little bit of wiggling. You should tighten the lock nut each time you do this as it may affect the final adjustment. If you tighten the lock nut and find that your lash setting has changed tighten the adjustment screw a bit to compensate, re-tighten the lock nut and check it again. Usually after I do all of this, and I am satisfied with my setting, I then take the next larger feeler gauge (.003) and try to insert it into the gap. If it doesn’t fit great I move on to the next one but if it slips in I readjust the lash until the correct sizes slips in fairly easy but the next size up wont go in. You may wonder why not just set it a little tight and not worry about it? I like to set these things exactly as needed for the best performance. The other reason is the way that motorcycle engine valves wear. Very rarely is there any wear at the top of the valve, most of the wear occurs where the valve closes at the valve seat in the head, this causes the valve lash to get tighter as the engine wears & not looser. This is especially problematic when you are running old motorcycles on the toxic, corrosive, & environmentally unsound corn juice that passes for gasoline in this day & time. If you must err on the side of caution it would be a little tiny bit better for your valve lash to be just a hair too loose than to be to tight.

For really thin feeler gauges like this .002 I recommend a holder like this one from Snapon tools.

Next take the .003 feeler gauge & set the exhaust valves as shown here. Then use the .004 gauge to make sure your adjustment is just right. It is especially critical not to over tighten the exhaust valve lash. If the valve wears down and is not able to close all the way due to a lack of clearance you may get a burned valve & a big repair bill.

If you have a late 70s or early 80s Honda with the factory electronic ignition you definitely want to perform this next step. First get yourself a set of nonmagnetic feeler gauges. DO NOT not use steel feeler gauges to set the magnetic pickups aka pulse generators on these bikes.

Non-magnetic feeler gauges are a necessity to set air gap on the pulse generator of most OEM electronic ignitions of this time period.

The range of settings for the air gap between the pulse generators (black boxes in the picture below) and the trigger mounted on the end of the crankshaft is .012-.016 inches (0.3-0.4mm) You can also see the pointer & the timing marks that I mentioned above in this picture.

1980 CB650 timing marks, pulse generators & advance plate

Believe it or not I have never seen any motorcycles with this gap set correctly from the factory, but the system is still good enough so that most bikes run without any problems whatsoever. Still if you have one of these and it runs okay except for a little surging & hesitation the pulse generator air gap should be the first thing you check. To set mine I just rotate the engine until the trigger ( little square nib sticking out of the crankshaft ) is aligned with nib on the pickup, loosen up the adjustment screws, stick the feeler gauge in place, & hold it all together while tightening the screws back down. Then rotate & repeat to do the other one.

This makes a huge difference in engine performance if it is set correctly.

There you have it, put a little lube on the advance mechanism behind the plate, reinstall all of your covers, spark plugs & fuel tank. Now it’s time to fire it up & check it out. Once you are sure that you did everything correctly & your engine is sounding just the way it should take it out for a ride & enjoy the fruits of your labor!

Peace Y’all

Revenge of a Junkyard Dog! (Suburban Assault Scrambler Finished!)

It seems hard to believe that it has already been six months since I dragged home a rusty non running 1980 Honda CB650 Custom that I bought sight unseen at a local junk auction for the princely sum of 150 bucks.  If you didn’t see it back then click on this link to see the before pictures. Of course along the way there were various challenges & fun but I had a blast getting this one going and as unlikely a candidate as it was for a scrambler conversion it really did turn out that the whole was greater than the sum of its parts!

Normally I am a man of way too many words so how about if this time I just show you some pictures interspersed with a few tidbits of technical information?

1980 Honda CB650 with 1974 Honda CB750 gas tank & a set of 1979 CB650 standard wheels.

1980 Honda CB650 Custom Scrambler

The handlebars are courtesy of a 1970 Honda CL450 I just happen to have lying around. The tires are Shinko 705 adventure touring tires.

I wish I had a plasma cutter like this at home!

The green paint is a mixture of gloss green & flat black tractor enamel, & the exhaust is from Mac.

they don’t make machines like this vintage Lincoln welder anymore.

Don’t let the nasty looking lowers fool you, the forks have new seals, Progressive Suspension springs & fresh 10w fork oil. I decided to keep the 650 Custom fork legs for the scrambler conversion since they are longer than the 650 standard forks. When I raised the rear by switching to the 17 inch wheel & taller tire it helped to compensate for the extra rake of the custom and gave more ground clearance.

At this time I would like to give thanks to the wonderful folks who provide me with my day job that makes all of this possible.

Safe Harbor Access Systems for allowing me use of the old warehouse and some production areas for this photo shoot. Click here to see the stuff I spend all day drawing blueprints for! And if you see anything you need let them know where you got the information.

Here’s some more of that headlight bracket drillium that I showed you in my last post.

speed holes make it faster right?

I couldn’t stand the 85 m.p.h. speedometer that came on this bike, plus it was making a horrible squeaking sound, so on went the 140 m.p.h. speedo & tach from a 1976 CB750F, with green faces of course.

Do you have any idea how hard it was for me not to attack this with the polisher?

K&N air filters hang off the back of the original carburetors, to learn what I did to them just click here. Other than a re-jetting

& a Mac pipe the engine is bone stock in all of it’s 11,000 original mile glory.

Slug & liquids? Sounds like the results of cheap beer & too many hot wings…

I put a lot of speed holes in this one ’cause I wanted it to be really fast 🙂

Holding up the rear is a set of Progressive Suspension 412 shocks with the heavy duty springs. I have been very pleased with this suspension, it gives a nice cushy ride over some pretty rough bumps but is still firm enough to rock out on a set of curves. Well at least as much as you can with a bike like this.

Sometimes you just find the perfect graffiti to really set a picture off.

Beware of the Dog

Peace Y’all

‘Psyco

A Custom Battery Tray & Other Stuff

Just thought I’d do a quick update on some of the things that I have done with my CB650 project. I have been working on it a little at the time between my normal day job, a few bikes & atv’s for other people, & some painting (airbrush practice & landscape oil painting). Since I’ve decided to go with the “rat suburban assault scrambler” look some of the things about this project have gotten easier, but other design ideas require just a little more ingenuity. Rather than sawing off the back half of the frame & welding in a new seat loop as required to get the proper cafe racer look I am opting for a modified stock seat with a 74 CB750 tank, but I still wanted to eliminate the stock side panels. My plan now is to replace the side covers with 2 pieces cut from some rusty old expanded metal sheet I have lying around. To do that I still needed to modify the mounts for the electrics, and since I will be using a Shorai lithium battery that is much smaller than stock, a custom battery tray was in order also. Since this is a rat I decided to do this with nothing but materials I already had on hand. After sitting down & staring at it a while with my note book, pencil & ruler in my hand I came up with a basic design that tucks everything up high, bolts into the stock mounts, & allows me to reuse the inner fender to protect the electronics. Here’s how it goes…

First I removed the stock battery tray, along with the airbox & some other now useless items. Then I drilled out all of the spot welds holding the mounts, & various brackets to it.

butchering a Honda CB650 battery box

In the spirit of my deep back country roots I decided to make do with the stuff I had on hand & not buy any new stuff to make this from, so this left over shelf divider that was destined for the scrap bin will get to live on as a motorcycle part. Here it is with all of the brackets & mounts salvaged from the original battery box.

a custom battery & electronics tray in kit form 😉

Then using my band saw I cut the tray to shape & bent it in a vise.

Then I bolted the stock mounts back into place using the original hardware & clamped the tray in between them. Since I do not have a tig box for my welder (YET) I simply use a 1/16″ 6013 rod to tack the pieces together without burning through the sheet metal too much.

tack welding battery box

After I got it tacked together with the stick welder I took it out and flipped it over & then brazed it securely together with the oxy-acetelyne torch. Then I laid out the various components such as the rectifier, turn signal flasher & etc & then brazed those mounts to the bottom of the plate.

custom rat motorcycle electronics mount

I know it looks awful, but I might just leave it that way, this is a rat after all. I will have to sort & secure all the wiring though, because neatly sorted wiring is easier to trouble shoot in the future & is less likely to develop problems that need trouble shooting.

Here’s a view from the top side showing the Shorai battery lying on it’s side. I still need to make a plastic box to keep the battery from sliding around. Since my day job is doing design work using Solidworks, I may just draw one up & have it printed out using a 3d printer. If not I’ll form one out of ABS sheet.

fits just right!

I can’t say enough good things about these batteries, they’re light, powerful & durable. I’ve installed them in a couple of customer bikes, this one, and even have one in my lawn mower! Sure the cost a little more than the lead acid batteries, but are in my opinion a threefold improvement in all areas. I do sell these & would be happy to quote you one if you contact me.

Here a couple of other items that have been added, first an Ebay find of a 74 Honda CB750 fuel tank. This fit with modified rubbers & a custom rear mount. I’ll show you some more details later after I have it all worked out with the seat fitment. but I think it looks really good on here!

Honda CB650 with CB750 tank

Another Ebay purchase is this 1970 Honda CL450 Scrambler. I bought the whole bike just to get the handlebars!

1970 Honda CL450

It’s pretty much seized up and there’s no paper work but the handlebars gave me exactly the look I wanted for my project. Good solid bars with just enough crust to blend in. No need to treat a new set of bars to a faux patina.

1970 CL450 handlebar on 80 CB650

The CL450 will be parted, I plan to keep the frame, engine, carbs, gauges, charging system, fork & wheels. All of the sheetmetal and the exhaust are up for grabs to my fellow hobbyists who want them. The fuel tank is rusty bondoed junk but everything else is decent. Contact me using the form below.

I had a few other adventures including dealing with a stuck oil filter bolt that I’ll go over with you soon including how far I had to go to get it out.

Peace Y’all

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Oil Sump & Strainer Cleaning

Alright! You’ve got your latest barn/field/junkyard find home, it still had good compression, so after cleaning the carbs, topping off the oil and putting in fresh gas it actually fired up and ran okay. Yeehaa! now comes the hard part, do not immediately go running in the house to scour the internet looking for the thousands of dollars worth of parts & accessories you need to restore or customize your new to you machine, there is one more thing you must do to be sure that you don’t need to tear the engine down to bare cases, or perhaps just throw the whole damn thing in the trash. Most vintage Japanese & British machines have an oil sump (oil pan to some of you) strainer, that has probably never even been looked at since the machine left the factory. For this lesson we are going to remove the oil sump (pan) from my personal 1980 Honda CB650 and see what we find inside. After a few minutes running time  & a valve adjustment this old thing has less the 8 p.s.i. difference in compression from the lowest to highest cylinder, I can live with that, if there is nothing wrong in the bottom end. Lets have a look shall we.  First if you have a lift put it up on the lift securely.

Let the serious work begin!

The mufflers are off of mine because I am planning on binning them anyway, it is not necessary to remove them for this job on this motorcycle.  On some bikes it may be required, refer to your service manual for details.

Locate the oil drain plug,

the location of the drain plug & oil pan bolts

and remove it with the appropriate wrench and drain the oil into a catch pan.

be sure to catch the aluminum sealing washer.

Since this involves changing the oil you might as well go ahead & change the filter too. On these old air cooled Hondas the filter is a cartridge in this housing on the front of the engine.

Oh no! this bolt has pliers marks on it. Not cool.

Remove the filter and housing, be sure to move the catch pan so that it catches the oil from the housing.

removing the oil filter bolt

Now move to the bottom of the machine and begin loosening the bolts on the sump. The CB650 has 10 bolts that are all the same size & length, so all I have to do is don’t lose any. If you motorcycle has different size or length bolts holding the sump on be sure to note which bolts go into which holes.

the motopsyco hard at work

Before you completely remove the last bolt and thus the sump be sure you slide the drain pan back into place beneath the engine.

Before you rush to dump the oil pan set it on the bench and have a good look at the goo stuck in the bottom of it. This will tell you a lot about the health of your engine. Believe it or not the crappy looking mess in the picture below is actually what you hope to find.

inside the CB650 oil pan

This one has a thick coat of clutch dust & what ever dirt that got into the engine & settled out of the oil, what I don’t see are any pieces of gear teeth or metal shavings that indicate an serious problem with the engine or transmission. Now take a magnet & swish it around in the muck to see if it picks up anything. Mine came back clean this time. This is no 100% guarantee that all is well with the transmission etc. but it does make me feel better about buying the parts needed to get it ride-able.

Now it is time to inspect & clean the strainer screen.

location of oil strainer Honda CB650

While you are down ther3 have a peek up into the engine to see how everything looks.

this all looks good in here

On a CB650 slide the drain pan back under the engine & pull down on the strainer, it should slide out.

just pull it straight down.

Once you get it out carefully inspect the screen and if it is damaged or loose replace it. If it looks good wash it out in the parts washer.

Inspect the strainer & its o-rings if you have any doubt about their condition, replace them.

Now you just have to clean everything up inspect & replace all gaskets & o-rings as needed, and reassemble everything in reverse order installing a new oil filter & fresh oil. NOw you know that you have one less thing to worry about.

Peace ‘Yall

Why Can’t I Let Dead Dragons Lie?

What I see anytime I see an old Japanese classic left to rot…

Here we go again, I knew this old Honda was bad news the first time I saw it. Years of abandonment & sitting out in the weather had taken a severe toll on every single piece of it, how often do you see a rust hole in the top of a gas tank?

To make matters worse it is a 1980 model the first year Honda started using that sway backed horse looking frame designed to get the seat closer to the ground in hopes of getting more people into riding and thus increasing sales. And yet here it is sitting on my lift as I am evaluating its potential as a custom possibly a cafe racer. The S.C. inspection sticker on the fork is dated 1988, and this was probably the last time it was on the road as S.C. did away with inspections soon after. The carb float bowls were completely gummed up and one slide was frozen in its bore. But the residue cleaned out okay and corrosion was minimal leading me to suspect that it was pre-ethanol gasoline in the carburetors!. It actually fired up and ran after a fast & furious carb cleaning. Heck I even wire brushed the original spark plugs and stuck them back in as they all 4 spit great big blue sparks during my initial testing.

It actually was kind of anticlimactic, this ancient corroded cobweb covered corpse fired right up and ran like a Honda. I felt like some  necromancer in a fantasy story that had prepared a powerful magic spell to reanimate the dried bones of a dead dragon only to have it sit up, yawn and say, “well that was a nice little nap,” before I could cast my spell.

It did smoke a little but there were no strange noises, not even a cam chain rattle. Since the engine is very rough looking cosmetically and I like to be as close to 100% sure about my motorcycles as possible,the next step in this evaluation is to pull the engine from the frame & take the head off and have a look inside. If all looks fixable I start renewing this bike in earnest beginning with an engine overhaul.

Although I try to kid myself that I am still evaluating this thing, I did purchase a set of wire wheels that I spotted on Ebay at a good price, & to crank it up I bought a new Shorai LFX battery for it. Experience tells me that I should wind up with around 3-4 thousand dollars in a motorcycle that might be worth 2 grand at the most. :O

Shorai LFX the best motorcycle battery money can buy.

Help here I go again 🙂