Topic: Building of a CB500 classic racer

[cdoggy81]

wow, great build!

[Howell]

Today I received a package from the US , Dyna 3 Ohm high voltage coils (35000 V) and sparkplug wires , bought on Ebay.
Tomorrow I will fit them and then in the weekend we will do a testrun on a nearby country road.
I hope this set of coils prevents us in the future for the loss of revs we had the last races.

[Howell]

Some threads ago I mentioned the shifting problems we had , shifting from 4th to 5th went difficult.
Now I know what this problem caused.
Last weekend we had a race in Germany, the bike was running very well with the new Dyna coils and other heavier clutch springs.
But after the second timepractice Yrjo said that the 3rd gear was missing , it wasn't possible to shift to the 3rd.
So he had to shift from 2 to 4 th gear losing a lot of time.
I checked the complete shift mechanisme by removing the complete clutch because the shift drum wouldn't rotate easely.
But there was nothing to see from the outside.
So I removed the oilpan and inspecting the gears, I saw that the undercut dogs of the 4th gear were worn down.
What caused this ?
We had no spare to fix it and decided to go into the race next day without the 3rd gear.
We had two races at the same day.
First race:The track was wet because of bad weather during the whole weekend, but just before the race the rain stopped.
Yrjo made a good start and was riding after three laps on 8th place, but next round  I missed him.
After a short time he came back with the bike and told that also the 4th and 5th gear were missing.
Over and out for that day, no points for the championship for us.
Yesterday at home I opened the engine and found the cause.
The gearshift fork for the 4th and 3rd gear was jammed on the shiftdrum, so the fork couln't shift enough to push it into the right gear.
I don't now why this happened.
Removing the fork from the shiftdrum went very difficult.
From the 4th gear the dogs were worn down also the 3rd had some wear.
So I emailed immediately Ellis Moore with some photo's of the damage asking if he had new gears in stock.
Ellis responded today just before he went to the Isle of Mann for the Manx grandprix that he has the 4th gear in stock and that the wear on the 3rd was not so bad that I have to replace it.
I asked to send the new gear after he is back from Mann.
We have some time left because the next and last race of the season is over three weeks.
Some picture of the damage:

[scottly]

I checked the complete shift mechanisme by removing the complete clutch because the shift drum wouldn't rotate easely.

Removing the fork from the shiftdrum went very difficult.

Is there a lack of lubrication to the drum? With the parts out of the transmission, does the fork slide easily on the drum? What does the "pin" that follows the groove in the drum look like?

[turboguzzi]

hi howel

i wouldnt be surprised if what caused the damage was the bad angle of the gear arm that you been using before. if the dogs were not going fully in, then they start to create pressure on the forks under power and that could have jammed the fork.

did your son feel any improvement in shfiting with the new arm geometry?

TG 

[Howell]

hi howel

i wouldnt be surprised if what caused the damage was the bad angle of the gear arm that you been using before. if the dogs were not going fully in, then they start to create pressure on the forks under power and that could have jammed the fork.

did your son feel any improvement in shfiting with the new arm geometry?

TG 

Hi TG,

It is of course possible that the bad angle caused the damage.
You can see on the fork that there was much pressure on it.
The new arm geometry gave no better feeling then before.

[Howell]

I checked the complete shift mechanisme by removing the complete clutch because the shift drum wouldn't rotate easely.

Removing the fork from the shiftdrum went very difficult.

Is there a lack of lubrication to the drum? With the parts out of the transmission, does the fork slide easily on the drum? What does the "pin" that follows the groove in the drum look like?

We had a good lubrication on the drum , there was a lot of oil between the drum and the fork..
As I said the fork jammed on the drum and wouldn't rotate , I had to crack it off.
The pin follows the groove very well.

A look at the crankshaft now the engine is open:

[Howell]

Today I received the new 4th gear from Ellis Moore.
See the difference between the old and the new one.

[DresdaHonda]

Hello Howell
-As us sure know I'm a beginner in Honda 500 engines

But I'm Benn working on BSA B50 gearboxes
-I have a extra engine BE with big holes in it, so it possible to see how the gearbox work

When I shim it, and try again

Dresda

[Howell]

No 13 ?

Bad race weekend.    

This weekend was the last race in Assen for the Dutch classic championship.
We went full of confidence there after the gearbox troubles we had.
We would like to finish in the top ten of the championship, that was possible.

Practice 1:
Saterday : After 3/4 lap in the first practice Yrjo came into the pit , he told the engine made suddenly a lot of noise and wouldn't rev higher then 8000 rpm.
It seems the noice came out of the cylinderhead ,se we went to the paddock to examine it.
We removed the cylinderhead cover , but I still found nothing untill we removed the cam and then I found a broken camchain tensioner.
We had no spare , but our college classicracer and Honda dealer Frank Lemstra had a new one for us.
We put in the new one and started the engine again , but there was still a scraping noise.
Did we made a mistake putting in the new tensioner.
I decided to remove the cylinder head cover again to inspect it but found nothing wrong and removed also the cylinderhead to inspect the valves and pistons.
Everything looked well  with the cylinderhead and pistons.
We had to take a closer look and therefore I removed the clutch , but eventhere was nothing wrong.
Finally I removed the oil and oilpan and found metal and copper particles in it.
 I think it is a bigend bearing of one of the bronze pistonpin bushings.
So end of the last raceweekend for us , we packed our things and went home sundaymorning .
Our goal to finish in the top ten was over , now we are on 13th place in the overall ranking.
I put the bike in the garage and will take it apart after two weeks holliday in the south of Frence to recover from the mechanical stress  

Our friend with the nr. 5 (first nr 46) bike finished 4th in the race and in the championship and that with the same kind of engine.

Also our friends from the UK , Colin Stockdale and David Martin were again in Holland and finished 10th and 14th.
Now we have more then six month till next year championship to overhaul the complete engine.

[turboguzzi]

hei rene

too bad.... hope that next year goes better, you will sure know more about cb500 motors now

your two problems seem unrelated, unless the little piece missing from the tensioner went inside the motor.

can recommend the hornet 600 tensioner i am using, its so much sturdy than stock.

I know your friend had good reliability with the same motor, but maybe he has also the experience of running it for a few seasons? What I am trying to say is that maybe you could take a step back to a more standard motor that maybe will casue less "surprises".

TG


 

[Howell]

hei rene

too bad.... hope that next year goes better, you will sure know more about cb500 motors now

your two problems seem unrelated, unless the little piece missing from the tensioner went inside the motor.

can recommend the hornet 600 tensioner i am using, its so much sturdy than stock.

I know your friend had good reliability with the same motor, but maybe he has also the experience of running it for a few seasons? What I am trying to say is that maybe you could take a step back to a more standard motor that maybe will casue less "surprises".

TG


  

Hi Yossef,

I couldn't wait to open the engine after my holliday , so I did it this afternoon.
And as I expected the crankshaft and bigend bearing are damaged , particular on the right side.
One of the conrods has became blue at the bigend.
Although there was enough oil at the bearings when I opened the engine , there must have been a failure in the oil supply.
The tuner thinks that this happened after the rebuild with the new gear , when starting the engine again.
Although I started the engine after the rebuild on the paddock starter without ignition on , to pump the oil all around and after a few seconds starting with ignition on.
There must be left a lot of air in the oil gallery's and oilcooler hoses he thinks and then you have no lubrication for a while which can cause damage.
This winter we had already planned to inspect and change al the crankshaft and bigend bearings if neccessary.
Our friends bike is indeed more reliable then ours with the same specs , we interchange al the experience with the engine to each other , we have no secrets , I think it is just bad luck we had.
I have n't found the missing piece of the camchaintensioner maybe this missing piece is grinded and has caused the damage.

[turboguzzi]

have a hard time to believe that the damage was because of some air in the lines.

I had a few experiences that clearly show that the pump output is very very high so the lines fill in a matter of seconds.
when i first mounted my external oil lines, turning the engine by hand for just a few revolutions would have oil coming out of them even if empty.

on another occasion, i mounted the oil check valve backwards and just after two seconds, the high oil pressure cracked the oil filter cover and sent a nice "spritz" up into the air. so if you turned the engine a few revolutions with the starter, your lines would fill in no time.

have you disassembled the oil pump to check for damage? maybe bits of the tensioner got inside? the fact that you cant find the broken piece is not a good sign.... regretfully, little things dont get lost inside the motor

TG

[simon#42]

i cant see that damage being due to air in the system either howell , bearing clearances a bit tight perhaps?

[Howell]

i cant see that damage being due to air in the system either howell , bearing clearances a bit tight perhaps?

No , not to tight , because also the bigend bearings are damaged and I did n't pull out them.
Only the crankcases were separated and I mounted the bolts with a torquewrench.
 

[Rod]

I had a few experiences that clearly show that the pump output is very very high so the lines fill in a matter of seconds.

+1 if the pump is ok, air in the lines is not the problem

[Sam Green Racing]

Rene, It won't be an air lock. Even in a dry build with just build lube, the air gets dissplaced very quickly with just a few turns of the crank.
Are you sure the shell didn't move when you had it apart?

Sam.

[Sam Green Racing]

Rene, after looking at your pictures an reading your/Yrjos report, I don't think you had a lubrication problem from the start.
If you had, it would have probably shown up during warm up (5-10 minutes) not 3/4 of a lap later under power.
The tensioner failing would account for the noise, it would also account for the loss of revs as would the crank tightening on the mains and big ends.
I think you have more than likley got some debris from the tensioner that has caused the pump to fail or maybe some fine particles have got through the screen and through the pump, damaging it and the crank/big end bearings.
Have you not got round to checking the pump and screen yet?

Sam.

[Howell]

I just opened the oilpump and found scuffing in it and very fine particles.
I think now that these particles are from the missing piece of the chaintensioner.
See the pictures:

[Sam Green Racing]

Was the screen damaged Rene or was the mesh large enough to let fine particles through?

Sam.

[Howell]

Was the screen damaged Rene or was the mesh large enough to let fine particles through?

Sam.

The screen is not damaged but the mesh is indeed large enough to let it through.

[Sam Green Racing]

 

[simon#42]

at least you now know what has caused the problem ,  new oil pump , crank , rods and the hornet cam chain adjuster that tg recommends and your back in business . that was quite an expensive cam chain tensioner though

[iomtt9]

Sam, i'm with you on Renes problem. It seems very bad luck that no 4 big end has failed and also no 5 main bearing.
I tend to agree with you that maybe he has dislodged no 5 main bearing when he had the new gear in.
The pump body and rotor look very scored which could mean loss of oil pressure but no bits would have got through
the oil filter to get to the no 4 big end.
When he gets home i would like to see the top of no 4 piston. Dave Martin and i have had our fair share of blow ups,
and that sometimes happens when you are racing a 38 year old bike. I keep asking him to come to England and do a
CRMC meeting as most of the Dutch meetings are only 1 x 12 lap race, Snetterton 3 weeks ago we had 8 races in the weekend !!!!
I hope he has a good holiday and gets stuck into the Winter rebuild........

[turboguzzi]

yep, looks like pump had some bad food....

check also your gearbox teeth, maybe it's them who turned the broken piece into dust

I know its easy to say this with hindsight, but you shouldnt have restarted that engine if you couldnt find the missing piece... things can get jammed in the gearbox too and then a blocked rear wheel will really hurt.

Lost once a camshaft chain safety circlip in the engine, a magnet couldnt find it, neither was it in the oil pan. ended up turning the whole bike upside down and it came out at the end.

tg