Jap Technical

[spinkox 37]

Anybody old or wise enough to know what the maximum revs are on JAP engines??

[cpbyles 0]

Anybody old or wise enough to know what the maximum revs are on JAP engines??

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Question is a bit vague ....... which JAP engine ?

 

Lets start at 1930/31 .....

 

A test procedure was devised in which each engine would run for four hours at 3,800rpm, after which it would be run on full throttle for ten minutes. It was expected that under these circumstances, each engine would record a minimum of 37.8 bhp at 5,750rpm, this being the peak of the power curve. the valve timing having an overlap of 78 degrees.

 

Got a feeling this thread could progress very slowly

[spinkox 37]

Question is a bit vague ....... which JAP engine ?

 

 

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Actually im asking this question on behalf of my brother . . . I didnt think the design changed all that much. He bought the engine at an auto jumble - so could be even he doesnt know exactly which engine it is. Does anyone have a list that relates engine number to date?? Will post more info when i obtain it. Interesting what you say tho . . .

[cpbyles 0]

Does anyone have a list that relates engine number to date?? Will post more info when i obtain it.  Interesting what you say tho . . .

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Assuming it's a Speedway engine, then yes, I have list relating to engine numbers

giving year and type etc

[spinkox 37]

Assuming it's a Speedway engine, then yes, I have list relating to engine numbers

giving year and type etc

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ok . . .

This is the technical info i have:

 

Engine JAP 500 from Cooper racing car - 4 stud with the larger parallel fins.

Engine No. JOS/6 (or 5) 79609/4

with long alloy conrod

cam number 18989

127 degrees overlap

 

Hope this helps . . .

[colin 0]

ok . . .

This is the technical info i have:

 

Engine JAP 500 from Cooper racing car - 4 stud with the larger parallel fins.

Engine No. JOS/6 (or 5) 79609/4

with long alloy conrod

cam number 18989

127 degrees overlap

 

Hope this helps . . .

<{POST_SNAPBACK}>

 

From the Jap book that I have it states the following

J = 500cc side valve 80x90 bore & stroke

O = overhead valves (cancels the reference to side valve in preceeding letter)

S = Short stroke sportts engine (or special)

 

However the following mark(s) after the JOS/ should be a LETTER this refers to the year of manufacture.

Hope it helps a bit

I am sure there are more people out ther that know of these things!

Colin

[spinkox 37]

However the following mark(s) after the JOS/ should be a LETTER this refers to the year of manufacture.

Hope it helps a bit

I am sure there are more people out ther that know of these things!

Colin 

<{POST_SNAPBACK}>

I was told this engine could be 1948 - Can you say what the letter should be for that year??.

Maybe the people with JAP knowledge arent forum types . . . Presumably sombody out there has dates relating to Jawa engine numbers too . . .

[Topcat 58]

I was told this engine could be 1948 - Can you say what the letter should be for that year??.

Maybe the people with JAP knowledge arent forum types . . . Presumably sombody out there has dates relating to Jawa engine numbers too . . .

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Yes bring on the Jawa's too.

[bucket 0]

There is a listing of serial numbers for 2v Jawa engines at the bottom of this page here

 

I would also be interested in JAP engine numbers etc.

 

As for max. revs of JAP engines, in Chris Mortons book 'until the can ran out' he talks about a conrod breaking in a JAP he was testing and the flywheels doing about 8000 rpm when it happened.

 

2v jawa's max. rev at 8000rpm.

[colin 0]

I was told this engine could be 1948 - Can you say what the letter should be for that year??.

Maybe the people with JAP knowledge arent forum types . . . Presumably sombody out there has dates relating to Jawa engine numbers too . . .

<{POST_SNAPBACK}>

 

Hi Topcat

Well according to my book (J.A..P. The end of Era by Jeff Clew) the letter for 1948 should be a C.

So as it is written:-

Letters after the first oblique (year of manufacture)

P=1920,N=1921, E=1922, U=1923, M=1924, A=1925,T=1926,I=1927,C=1928,

S=1929,W=1930,H=1931,Y=1932,Z=1933,D=1934,R=1935,V=1936,F=1937,0=1938,G=1939.

These letters were later reused in the same sequence to cover years 1940 to 1959 inclusive, taking in to account the war years during which machines for civilian use were no longer manufactured. It is worth noting that the JAP production year ran from 1st Sept of the year previous to that identified by the dating letter , and ended on 31st August of the year indicated.

Max power is around 5700 to 6000 rpm it seems with 6300rpm being the the ultimate for the 350cc grass engine!!

Hope this helps in some way.

If you are interested in JAPS this is a worthwhile book to obtain!!

cheers

Colin

[Trackman 3]

"Haven't heard a J.A.P. engine for 40 years" or never heard one

Well you can hear one now !

Possibly a world first on a Vintage Speedway site, the burble of a J.A.P. 500cc engine in living sound !"

Go to http://www.justsolos.homestead.com/

Regards.

[Gemini 4,894]

We're very lucky at Coventry as we regularly get to hear the JAP engines in the second half. Certainly a lot louder than today's bikes which begs the question weren't there any NIMBY'S around in those days moaning about the noise like there are today?

[Mylor 0]

We're very lucky at Coventry as we regularly get to hear the JAP engines in the second half. Certainly a lot louder than today's bikes which begs the question weren't there any NIMBY'S around in those days moaning about the noise like there are today?

No.........back then they all went to the speedway!