Synchro conversion

fearsuminjin · Post by **fearsuminjin** » Sun Mar 16, 2014 1:37 am

Hi i am lead to believe there is an article on converting non synchro gearbox to synchro can you point me to it or give me some guidelines as to parts are required, the engine in my "Z" has an engine number beginning 20----- this cannot be the original as all UK spec z600's had synchromesh the original engine code should be 25----- any ideas as to what it originally came out of?
Thanks Alan

Don B Laughton · Post by **Don B Laughton** » Sun Mar 16, 2014 9:40 am

Humm, the "2" series indicates the "Z" engine with the cam cover with the narrow bolt pattern. All Z600s sent to the US had synchro transmission and metal vacuum piston carburetor, "25xxxxx" engines. The not so good news is you will need the complete main shaft and counter shaft assemblies, shift plates and forks. The first thing to check if the shaft bearings are the same and fit in the engine cases. Have you driven the car? Is it actually a non synchro engine?
Best wishes, Don Sent from my iPhone

On Mar 16, 2014, at 1:37 AM, wrote:
Hi i am lead to believe there is an article on converting non synchro gearbox to synchro can you point me to it or give me some guidelines as to parts are required, the engine in my "Z" has an engine number beginning 20----- this cannot be the original as all UK spec z600's had synchromesh the original engine code should be 25----- any ideas as to what it originally came out of?
Thanks Alan

Bill · Post by **Bill** » Sun Mar 16, 2014 11:11 am

Vehicles sold in some of the European countries had a no synchro trans there chassis numbers

Alan Stanyon · Post by **Alan Stanyon** » Sun Mar 16, 2014 12:47 pm

Thanks Don firstly yes it's the engine in the car i have been using for the last 4 years it is the metal type carb piston engine, its upside down in my workshop with the sump off, i have the synchromesh main and counter shafts ready to fit (i thought the cones were "worn out"), the selector forks on the non synchro box are smaller, good point about the shafts according to the parts list they are different (diameter?) is that true i dont know what diameter they are compared to the non synchro shafts i got talking to (i forget his name!) at the classic car show at the NEC and he had done it in the past and gave me the details the same as you have suggested ie selectors,selector shafts, shift plates,main counter shafts and crown wheel.
Alan To: 2cylinderhondas@yahoogroups.com From: dontranspac@...
Date: Sun, 16 Mar 2014 09:40:03 -0700 Subject: Re: [2cylinderhondas] Synchro conversion
Humm, the "2" series indicates the "Z" engine with the cam cover with the narrow bolt pattern. All Z600s sent to the US had synchro transmission and metal vacuum piston carburetor, "25xxxxx" engines. The not so good news is you will need the complete main shaft and counter shaft assemblies, shift plates and forks. The first thing to check if the shaft bearings are the same and fit in the engine cases. Have you driven the car? Is it actually a non synchro engine?
Best wishes, Don Sent from my iPhone

On Mar 16, 2014, at 1:37 AM, wrote:
Hi i am lead to believe there is an article on converting non synchro gearbox to synchro can you point me to it or give me some guidelines as to parts are required, the engine in my "Z" has an engine number beginning 20----- this cannot be the original as all UK spec z600's had synchromesh the original engine code should be 25----- any ideas as to what it originally came out of?
Thanks Alan

Bill · Post by **Bill** » Sun Mar 16, 2014 6:19 pm

Alan;
Don't attempt to use any of the components from the constant (non-synchro) transmission when switching over to the full synchro.

Miles · Post by **Miles** » Sun Mar 16, 2014 8:51 pm

Back in 1985 I drove a Honda Z600 from Fehmarn Germany to Hamburg on the Autobahn.
Then from Hamburg to the top of England. That coupe was purchased in England by my
friend Martin and it did not have synchromesh.
Miles

Alan Stanyon · Post by **Alan Stanyon** » Mon Mar 17, 2014 2:22 am

Thanks Miles perhaps the two i owned previously i thought were synchro boxes (it was 35 years ago) one i drove and the other came to me in wooden apple boxes, UK cars were different we have the heater drawing air through the cylinders to heat the interior for instance thanks for the input.
Regards Alan To: 2cylinderhondas@yahoogroups.com From: z600miles@...
Date: Sun, 16 Mar 2014 20:51:52 -0700 Subject: [2cylinderhondas] Re: Synchro conversion
Back in 1985 I drove a Honda Z600 from Fehmarn Germany to Hamburg on the Autobahn.
Then from Hamburg to the top of England. That coupe was purchased in England by my
friend Martin and it did not have synchromesh.
Miles

Don B Laughton · Post by **Don B Laughton** » Mon Mar 17, 2014 1:35 pm

Good news, almost, The upper and lower crankcases are the same for synchro and non synchro. If you have the synchro main and counter shafts, final drive gear assy, shift forks and plates, you should be good to go. Do you have the parts book? It should answer any other questions.
Best wishes, Don
On Monday, March 17, 2014 2:23 AM, Alan Stanyon wrote:
Thanks Miles perhaps the two i owned previously i thought were synchro boxes (it was 35 years ago) one i drove and the other came to me in wooden apple boxes, UK cars were different we have the heater drawing air through the cylinders to heat the interior for instance thanks for the input.
Regards Alan To: 2cylinderhondas@yahoogroups.com From: z600miles@...
Date: Sun, 16 Mar 2014 20:51:52 -0700 Subject: [2cylinderhondas] Re: Synchro conversion
Back in 1985 I drove a Honda Z600 from Fehmarn Germany to Hamburg on the Autobahn.
Then from Hamburg to the top of England. That coupe was purchased in England by my
friend Martin and it did not have synchromesh.
Miles

Bill · Post by **Bill** » Mon Mar 17, 2014 7:50 pm

Don;
I have made the change over to full synchro trans in a number of constant transmission Honda 600 using the early case. The lower case is almost the same, but in order to have the full synchro counter shaft to fit, the center fin (rear section) must be cut. Or the shaft will not fit.
Bill

Don B Laughton · Post by **Don B Laughton** » Mon Mar 17, 2014 8:13 pm

Interesting, the parts book only shows one set of cases for both types. Unless, my late book might only list a later common lower case. Should have checked to see how close the Honda codes are. (Honda codes are not entirely useless.) Sent from my iPhone

On Mar 17, 2014, at 7:51 PM, "Bill" wrote:
Don;
I
have made the change over to full synchro trans in a number of constant transmission Honda 600 using the early case. The lower case is almost the same, but in order to have the full synchro counter shaft to fit, the center fin (rear section) must be cut. Or the shaft will not fit.
Bill
From:
2cylinderhondas@yahoogroups.com
[
mailto:2cylinderhondas@yahoogroups.com
]
On Behalf Of
Don B
Laughton
Sent:
Monday, March 17, 2014 1:36 PM
To:
2cylinderhondas@yahoogroups.com
Subject:
Re: [2cylinderhondas] Re:
Synchro conversion
Good
news, almost, The upper and lower crankcases are the same for synchro and non synchro. If you have the synchro main and counter shafts, final drive gear assy, shift forks and plates, you should be good to go. Do you have the parts book? It should answer any other questions.
Best wishes,
Don
On Monday, March 17, 2014 2:23 AM, Alan
Stanyon wrote:
Thanks Miles perhaps the two i owned previously i thought were synchro boxes (it was 35 years ago) one i drove and the other came to me in wooden apple boxes, UK cars were different we have the heater drawing air through the cylinders to heat the interior for instance thanks for the input.
Regards Alan
To:
2cylinderhondas@yahoogroups.com
From:
z600miles@...
Date: Sun, 16 Mar 2014 20:51:52 -0700
Subject:
[2cylinderhondas] Re: Synchro conversion
Back in 1985 I drove a Honda Z600 from Fehmarn
Germany to Hamburg on the Autobahn.
Then from Hamburg to the top of England. That
coupe was purchased in England by my
friend Martin and it did not have synchromesh.
Miles