Peter Day

Yamaha FZR750R OW01  & YZF750 specialist

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Forum Home > General OW-01 Discussion > Japanese OW01 restrictions?

Lordmoonpie
Member
Posts: 20

I've heard all kinds of versions of what the restrictions are on a Japanese OW01 compared to a UK spec. version or even a European version. Some say that the CDI Needs changing from the Jap version to the UK version, some say the European is good enough, some say the restriction is not in the CDI at all and the Japanese CDI can be used on full power bikes? I've heard that there are some restrictors in the carb inlet diaphragms, some in the airbox compared to UK airboxes although having had both a Japanese and a UK airbox in my hands I cannot see a single physical difference. I've been told it's also jetted down compared to the UK bike and has additional restriction in the silencers. All of that seems too much like hearsay to me.

Does anyone know the true definitive list of restrictions on a Japanese spec. bike that stops it delivering the full power of a UK spec. bike? Any help appreciated. ;-)

December 29, 2013 at 2:54 PM Flag Quote & Reply

Pete
Member
Posts: 29

Hi, mine was restricted by webs accross the inlet rubbers and small jets. With theese bits put to uk spec the bike flies.


December 30, 2013 at 4:00 PM Flag Quote & Reply

Pete
Member
Posts: 29

Forgot to mention mine is a jap home market model 3 fv.

December 30, 2013 at 4:03 PM Flag Quote & Reply

Lordmoonpie
Member
Posts: 20

Thanks Pete - my bike is an oddity, I was told it was a Spanish import but it's clearly a 3FV and Japanese styled. It has no restrictions anywhere in the inlets and certainly flies already so maybe it's been sorted before my time? Appreciate your input ;-)

December 31, 2013 at 8:33 AM Flag Quote & Reply

Mark
Site Owner
Posts: 238

Lordmoonpie at December 31, 2013 at 8:33 AM

Thanks Pete - my bike is an oddity, I was told it was a Spanish import but it's clearly a 3FV and Japanese styled. It has no restrictions anywhere in the inlets and certainly flies already so maybe it's been sorted before my time? Appreciate your input ;-)

Hi Simon

Right here goes. TCI is not restricted (OWs run a transistor controlled ignition, not capacitor)

I run a 3fv ignition module on my race bike and that makes plenty of power:D.

Exhausts are the same, should be no restriction there.

Airbox should be the same.

 

What you are looking for is webs in the inlet rubbers between the carbs and the motor, just like they used to put in exups to slow them down. You can change the rubbers for UK ones or cut them out neatly and carefully with a scalpel.

PLUS you need to check the carb tops, above the diaphragms., as sometimes they have a stopper in there that stops the slides lifting too far.

And yes, these bikes are also downjetted to suit, so they run cleanly.

So you need to sort the above, then book some dyno time to get it fuelling correctly so you don't burn out your exhaust valves from lean jetting.

The other thing is that the 3FVs run a smaller rear sprocket (43T instead of 46T) Probably to drop the revs in drive-by noise testing. This is WAY to high, makes the bikes feel like slugs, and accounts for all 3FVs Peter gets through the door having knackered clutches!

Hope this helps

 

Mark

December 31, 2013 at 11:41 AM Flag Quote & Reply

Pete
Member
Posts: 29

Forgot to mention mine had a smaller rear sprocket too but the front sprocket has one tooth more than the uk bike so gearing works out to be just about the same and it should give the chain an easier time.

On a slightly different tack the two unused wires under the seat on the 3FV's are not to do with the restriction, I have recently got a genuine Yamaha 3FV workshop manual and the wires seem to be conected to the speedo via a sub loom and then on to a bulb so I presume this is for a speed warning lamp on some models.

 

 

January 3, 2014 at 5:23 PM Flag Quote & Reply

Mark
Site Owner
Posts: 238

I think youre right Pete. I had an FZR400 a few years ago (when I was young!!) with a red speed warning light in the dash. It came on above 55 mph. I used to commute on that bike, and in the dry, the mission was to not let the light go out any more than 5 times on my route to work!

Im not sure that was the intended use for the light... ;)

January 4, 2014 at 7:49 AM Flag Quote & Reply

Mark
Site Owner
Posts: 238

BTW Pete, One tooth more on the front sprocket RAISES the gearing, not lowers it. Maybe yours was a typo.

 As a rule of thumb, a change of 1 tooth on the front equates to approx. 2.5 rear teeth...something I used to exploit with TZ250s when we were "half a tooth" off perfect gearing.

January 4, 2014 at 7:53 AM Flag Quote & Reply

Ray916MN
Member
Posts: 3

I've ust derestricted my Japan market bike. What are the jetting changes that need to be made?

September 23, 2018 at 8:39 PM Flag Quote & Reply

OW01-Rick
Member
Posts: 3

Ray916MN at September 23, 2018 at 8:39 PM

I've ust derestricted my Japan market bike. What are the jetting changes that need to be made?

Carb settings on both my OW01s: Main jets -- #117.5 inside and #122.5 outside ( Japanese Model) STD air box -- #137.5 inside and outside (US Model) w/ individual K&Ns. To derestrict your Japanese model you air box has a plug (easy to remove) your boots are restricted with a flap, cut out the flaps cleanly. The EXUP valve open only partial at full throttle, so that will need adjusting. The stock CDI box (8-8.5K RPM MAX) either needs to be replaced with a Sugo Kit or standard /UK unit or do some very carful surgery on the Jap-spec. unit.
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OW01-Rick
October 4, 2018 at 4:56 PM Flag Quote & Reply

Harry
Member
Posts: 10
Is it just me or can no one start a new topic, wonÂ?t let me just says r1capture
October 12, 2018 at 4:12 PM Flag Quote & Reply

Rich
Member
Posts: 157

Yep, I see the same

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October 13, 2018 at 2:08 PM Flag Quote & Reply

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