Author Topic: splitter's 1974 CB500 (Read 5754 times)

splitter · « **on:** February 25, 2019, 11:56:15 am »

I'm continuing the topic on my CB500 Four here, after small introduction in 'New Member Introductions' forum. The plan right now is to get the bike on the road for the coming riding season (starting from April) here in Estonia.

Info about the bike.
I purchased this beauty from Finland in September 2018. I believe it to be an European K1, but as I know these European export models were assembled with parts from various production years. So in US standards it’s not a pure K1, more like mix of K0/K1/K2. Some parts have certainly been replaced as the bike has seen some smaller crashes and a repaint.

It’s first registered in April 1974 but model year is still probably 1973. According to the papers the bike has done over 104 000 kms. I’d figure that the engine has seen an overhaul sometime during these kms? When I went to see the bike it was running on three cylinders, front brake was sticking which made the clutch slip a bit and the tires were almost 20 years old. When the engine warmed up, some small oil leaks came apparent. The PO said that the bike had been basically been sitting for over 13 years. I still liked the looks and the feel of this CB500 and ended up buying it.

Sticking front brake ended up being a blocked pressure relief hole in master cylinder. Ended up flushing and cleaning the whole system. All the seals and pistons looked really good on both master and slave.

I pulled the carbs and cleaned them. Carburetor for cylinder #3 had a clogged idle jet and all of the float bowls were full of petrol residue (resin-like substance). Rubber boots which connect the carbs to the intake manifold were hard as a plastic.

Replaced spark plugs and caps, cleaned air filter. I also bought NGK J1 cable splitters as the ignition wires were falling apart between my hands. Tires are now Heidenau’s K36 (rear) and K44 (front).

After doing a small tune-up (adjusting timing, valve clearance etc) I got it to run on all of the four cylinders. I drove it around for few hundred kilometers to get a feel for it and I started to experience more and more oil leaks and a ’lean hang’. Revs were not coming down to idle and synchronizing carbs became almost impossible. Also I didn’t like how the engine sounded (chains’ rattle) and clutch was not engaging smoothly. I took a decision to pull the engine before spring to check its overall condition and replace what’s needed (at least bearings, gaskets etc). Maybe do an overhaul to the carbs as well. Right now I’m about to move the bike into my man-cave to pull the motor. I would definitely appreciate your help on checking the common faults on the engine and finding parts.

Plans right now:

Take the motor apart and check its overall condition (and replace/repair what's needed)
Change all the seals/gaskets and O-rings
Change primary and cam chain, incl guides
Lap the valves
Rebuild the carburetors
Maybe upgrade to electronic ignition (new coils etc) to increase reliability???
Change the front fork oil
New front brake lines

splitter · « **Reply #1 on:** February 25, 2019, 12:05:47 pm »

Last night I managed to remove the engine. As soon as I got the motor on my work bench, it was obvious that the main culprit for the oil leaks it the head gasket.

First I drained the oil and had a peek into the transmission by removing the oil pan. First impressions were good for a high mileage bike. Primary chain doesn't seem to be too bad either but I will probably end up replacing it anyway.

At the moment I'm waiting to get my compression tester and measure the cylinders' before stripping down the top end.

Oil was really clean as the PO had done 'oil service' last spring. But the oil filter was dirty as hell, probably not replaced in 13 years... some small 'sparkles' in the filter casing but nothing serious.

bek1966 · « **Reply #2 on:** February 25, 2019, 12:29:21 pm »

I'm looking forward to following your progress! Nice looking shop by the way. I really like the wood floor - so much easier on the body and nice looking too.

Regards,
Brad

SOHC4 Cafe Racer Fan · « **Reply #3 on:** February 25, 2019, 02:56:12 pm »

The bike looks pretty good cosmetically. If you are going to go that far into refreshing the motor, change all of the seals, chains and gaskets.

Stev-o · « **Reply #4 on:** February 25, 2019, 03:01:46 pm »

Subscribed. What compression tester do you have? If automotive, dont expect accurate results.
If readings are within 10%, you are good.

Gurp · « **Reply #5 on:** February 25, 2019, 04:45:36 pm »

Subscribed

splitter · « **Reply #6 on:** February 26, 2019, 03:06:08 am »

Quote from: bek1966 on February 25, 2019, 12:29:21 pm

I'm looking forward to following your progress! Nice looking shop by the way. I really like the wood floor - so much easier on the body and nice looking too.

Regards,
Brad

It is actually PVC carpet but underneath it is still wooden floor. Wooden floor is really nice to work on and PVC surface is good for cleaning them oil spills and also dirt.

@Stev-o Yes, I have that universal automotive compression tester which has the one-way valve near the meter. I know that I will get lower readings but I only use the numbers as a reference. I will measure the cylinders and pistons anyway and check the ring gaps. I'm pretty sure that I have more than one leaky valve, judging by the heavy carbon deposits in the exhaust posts.

flatlander · « **Reply #7 on:** February 26, 2019, 08:34:34 am »

oy that's a nice one. if you get it to run well, it will be great.
just remove those mud flaps please

splitter · « **Reply #8 on:** February 27, 2019, 12:33:26 pm »

Had some time this evening and took the cylinder head off. Camshaft and its bearing surfaces look good, I will later measure the camshaft. While removing the 'valve cover' I noticed that the threads for two M6 bolts (out of four, under the breather lid) are stripped. Well, some helicoil will help me out.

Something has had fun in cylinder #2 sometime during the life of this motor. I believe the head is still usable but could use little skimming. I didn't have a flat bar in hand to fully check it.

Cylinder liners have pretty good hone marks on them. That was a pleasant surprise. Will check the piston ring gaps later on. If they are good, I will not re-hone the cylinders.

AND the main thing that made this rebuild worth it - heavily worn camshaft chain guides. Tensioner's plastic has pretty large cracks in it too. Note that shiny metal near the top of both guides.

Camshaft sprocket looks decent. Would you still replace it???

Damn, I'm missing a part of the lower crankcase, just under the breaker points. I don't have a good solution right now to repair it, I'm not sure I want to build it up with TIG welds. Could probably use a part from a scrap crankcase but it's impossible to find one here.

And that the state of the engine right now.

Next thing to do is to remove the valve and check the seats and guides. And I have to find a trustworthy machine shop to skim the head and lap the valves. I was also thinking about skimming the cylinder block's surface...All opinions are welcome.

Stev-o · « **Reply #9 on:** February 27, 2019, 03:19:35 pm »

Good progress. Your idea of "fun in the cylinder" is a lot different than mine! That looks ugly, a sure sign of a past issue. Personally, I would not use that head but I have spare motors and prolly not easy/cheap for you to get a replacement. I'd "skim" the head and cylinder and check the valve guides as well.

As far as the cracked case, you could try building it up with JB Weld or similar epoxy product local to you.

PS. Do you mind a personal question? Are you from Estonia? Your English is perfect!

jgger · « **Reply #10 on:** February 27, 2019, 06:13:11 pm »

They make an epoxy putty that you could use on the case. After it is mixed you have a few minutes to form it like clay. Then sand to shape and paint. It sets up pretty hard too.

754 · « **Reply #11 on:** February 27, 2019, 07:54:02 pm »

Yeah I would try JB or Devcon before welding.
Your valve spring top collars look changed.. maybe a spring kit.
Was It a stock cam ?

splitter · « **Reply #12 on:** February 28, 2019, 12:21:21 am »

@flatlander. I was waiting for someone to comment on the mud flaps

Actually I like the rear one, front is ugly as hell but still OEM.

@Stev-o. I do would get a better head if I could find one here and with a reasonable price. Will look into it. Still I see no reason why this head would not 'work'. OK, only if it's warped as hell I would scrap it.

Regarding that personal question (which I don't mind), yes, I'm Estonian, I live in Estonia and my native language is Estonian. Anyway, thanks for the compliment!

@jgger and Steve-o. Epoxy putty is a solution I have considered, I'll keep it as a last resort.

@754. I don't know about the springs or the cam, but if I remember correctly the cam had markings R12 and KE on it.

Korven · « **Reply #13 on:** February 28, 2019, 02:36:35 am »

Kinda looks like someone has been been sanding the sharp edges away.

splitter · « **Reply #14 on:** March 03, 2019, 01:06:37 pm »

Spent a few hours on this Sunday splitting the crankcase and checking various components.

Notes:
1. Crankshafts main bearings look all good.
2. No play in connecting rod bearings, will not disassemble them.
3. Gear shift forks's thicknesses all in limits and no sign of any damage.

All the rubber parts, that are in direct contact with oil, are hard as plastic. Did not get a single valve stem seal removed in one piece. Rubber dampers in primary drive gear were also 'plastic'.
When I removed the clutch, I noticed that clutch discs were sticking like glue to each other. Then I remembered that I once had an issue with clutch not engaging. Furthermore, discs' surfaces are a bit glazed I'd say, but the thickness' of the discs is basically like new (above 3.5 mm). I still think it is best to replace all the discs.

And the BIG question to you guys. What should I do with all the gearbox's roller/needle and ball bearings? Replace all or not? Needle/roller bearing show now visible wear or play. What I have learned is that most of the bearing in CB500's gearbox are are hard to find and pretty expensive, especially in Europe. Right now I think about replacing all the ball bearings and keeping the old needle/roller bearings. Good idea or not?

Cleaned the cylinder head, valves and cylinder block. Ready to be taken to the machine shop.

Notes:
1. Cylinder #4 had the lowest compression reading. I found that the exhaust valve's face (sealing surface) is pretty burnt and probably need grinding or I have to replace the valve. All the intake valves were good, but all the exhaust valves were showing signs of leak.
2. All but one, #4's, piston ring end caps were under 0.35 mm. The top ring in cylinder #4 had a gap of 0.72 mm. Will replace that.
3. Ring's side clearances were all good.

splitter · « **Reply #15 on:** March 14, 2019, 01:24:05 pm »

Haven't had much time to work on the CB. In the past week I got the cylinder head skimmed and valves lapped. Exhaust valves needed some work to get them tight. Machine shop had to take 0.12 mm off the cylinder head as it had a low spot near cylinder #2. Cylinder block's surface was also gone over, it only needed light 'sanding'. I have also been cleaning various engine parts and I have started ordering the spare parts. I still have to find a source for gearbox ball bearings.

splitter · « **Reply #16 on:** March 14, 2019, 01:31:05 pm »

I had some thoughts how to repair the lower crankcase as it had a missing piece below the points. I ended up fabricating a piece form fairly pure 3 mm sheet and got it welded in place. Tonight I spent an hour filing the welds. All in all it is not one of my best repairs on aluminum parts but I'm happy with the result as it was a really tight spot to get some decent welds in. Also the aluminium alloy of the crankcase was a bit different form the repair piece and that affected the weld quality.

splitter · « **Reply #17 on:** March 22, 2019, 12:59:24 pm »

I'm having trouble finding a gearbox bearing 5205 (NACHI), 91001-283-003 or 91002-283-000 . Anyone got a good lead where to buy one with reasonable price?

jaytee-nz · « **Reply #18 on:** March 24, 2019, 04:37:28 pm »

I searched the world (literally) for one of these when restoring my K1 CB500. Looks like they don't exist or a very rare.
In the end I used an off the shelf bearing from a engineering supply store and had the groove for the retaining clip machined in to it.
Is your bearing worn out because they do last for a long time unless the engine has been run short of oil ?

splitter · « **Reply #19 on:** March 25, 2019, 11:27:27 am »

It's actually not that bad. The whole internals of the engine are in really good condition, so are the bearings. Replacing bearings during engine rebuild is like a rule of thumb to me. I just want to do everything that I can to get the most miles out of this engine before next rebuild and tearing a otherwise good motor apart, just to replace a singe bearing, is also a thing I want to avoid. BUT, I have to agree that if the bearing is still good, it should last for years...I have to think about it.

splitter · « **Reply #20 on:** April 06, 2019, 11:45:38 am »

Last parts to complete the rebuild arrived on last Thursday. Now I have a large box of parts that need to installed, mostly O-rings and rubber parts tho

Anyway, started assembly with checking main bearing clearances with (red) plastigauge. I ordered brown bearings, as they are the "tightest" ones available and my engine had 3 pairs of browns and 2 pairs of greens installed from the factory. Measuring the journals and crankcase indicated that they are with same size. Would have loved to have blacks but with brown ones I got the clearances to about 0.04-0.05 mm.

Now, a question about gearbox. What's the allowed maximum axial play for this gear? Right now I'm having about 0.85 mm of axial play. I checked parts lists and they don't indicate that there are different thicknesses of it. No visible wear on thrust washes or mating surface on gear. Quite possible that it has been this loose from the factory as it doesn't affect shifting etc?! I used to having this kind of axial play in various gearboxes up to 0.1 mm.

I think in a few days I'm that far that I can assemble both halves of crankcase. What kind of sealant do you guys use between cc halves? I have previously used Reinzosil Universal Sealing Compound 3000 SI. It should be good for that application.

splitter · « **Reply #21 on:** April 14, 2019, 12:35:58 am »

Engine is back in the frame, yeah! As I bought new rear brake pads, replaced them before lifting the motor in place. Old ones had 4 mm of lining remaining and they will go into reserve.

Things left to do:
1. Install new ignition coils and Dynatek ignition.
2. Change front brake hoses.
3. Change fork oil.
3. Install exhaust system.
4. Rebuild (or clean) the carbs.

I ordered Keyster rebuild kits as they are the only true rebuild kits available. I've read so many mixed reviews about them, both good and bad. I at least need float valves from the kit but should I use all the brass or not? Which are the things that are 'wrong' with Keyster brass? Anything that I can notice with my bare eye?

calj737 · « **Reply #22 on:** April 14, 2019, 04:45:17 am »

Quote from: splitter on April 14, 2019, 12:35:58 am

3. Change fork oil.Much easier to do with the engine out than in.

Gurp · « **Reply #23 on:** April 14, 2019, 01:58:13 pm »

Interesting short lift.

splitter · « **Reply #24 on:** April 22, 2019, 12:45:32 pm »

I've been lazy and not updating this thread. But many hours spent reassembling the bike. The grand final was on Sunday when it fired right up and sounded sweet. Did some test runs and right now I'm happy how it runs and goes. Will give it a decent run-in period and eventually I'd like this bike to be dynoed and carbs/ignition fine tuned. I really like the looks of this bike and will share some pics.

News:

Author Topic: splitter's 1974 CB500 (Read 5754 times)