M1 jetting question

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M1 jetting question

Postby zxrmad » Wed Jun 08, 2016 2:32 pm

Hi all,

I own a '93 ZXR750R M1. When I bought this bike it had a set of CV carbs fitted and came with a set of brand new OEM FCR39's in a box. I'm now fitting the FCR39's and have a couple questions...

I was going to leave all of the emissions stuff on this bike, but as some of it is already missing, I'm just going to remove the rest of it. I'm confident that I know what to do with regards to removing the emissions stuff. But, what will I need to change in the way of jetting? I haven't opened the new carbs to check the jetting, but they should have stock jetting as they are brand new (never used) OEM carbs.

Anything else I need to know about doing this?

Thanks in advance
Current bikes... '93 ZXR750R M1, '95 ZXR750 L3, '95 ZXR750 track bike, '96 Bimota sb6, '99 Bimota db4, '08 Honda VTX1800, '94 Honda CB250, '00 Honda XR200, CBR400rr race bike, '49 BSA C10 250.
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Re: M1 jetting question

Postby greenman43 » Wed Jun 08, 2016 5:31 pm

Bolt them on and try them ! All jetting is individual, although it should be fairly close out of the box. That said, I once put a set of bog-standard FCRs on my L3 (full Yoshi and K&N), and it was pretty horrible down low.

Cheers,
Brian
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Re: M1 jetting question

Postby ZXRPI » Thu Jun 09, 2016 1:24 pm

Like Brian suggested, I'd bolt them on, too.

Personally I'd aim to bolt them on, get the bike to fire up and run, then get the bike on a dyno to sort jetting properly. Avoid big handfuls of revs or unnecessary running between getting it fired up and on to a dyno 'just in case' they are super lean out of the box.

Of course, I don't know your bike, and you may already know, but the OEM ZXR airbox mounting point on to CV carbs is different to FCR carbs - FCR's require a different airbox base that screws on to the OEM airbox. You should be able to see the slightly different part in a parts diagram explosion if you compare an L1 and M1. So, you will need to change this. Bonus if you have this part already!... and just some useless information if you have a different airbox altogether for the FCRs!

Cheers,
Dominic.
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Re: M1 jetting question

Postby zxrmad » Thu Jun 09, 2016 9:43 pm

Thanks fellas. Yeah, I've bolted them on and have run it but not ridden it as yet. I was just wondering if anyone had experience with removing the emissions stuff, I'm guessing (and from what I've read) it will be rich after removing all the crap, so smaller mains may be in order.

Dominic, The previous owner (Chris) of this bike had done a lot of hard work sourcing a lot of the missing parts as well as a lot of NOS replacement parts for the rebuild. Chris sourced the new FCR39's as well as the 'unobtanium' FCR airbox adaptor.

Some other very hard to come by bits that I have been lucky enough to benefit from Chris' hard work are... brand new close ratio gearbox, brand new titanium full race system, brand new Ohlins race spec FG8700's, spare M1 rear subframe etc, spare M1 bodywork.

Cheers,
Brian
Current bikes... '93 ZXR750R M1, '95 ZXR750 L3, '95 ZXR750 track bike, '96 Bimota sb6, '99 Bimota db4, '08 Honda VTX1800, '94 Honda CB250, '00 Honda XR200, CBR400rr race bike, '49 BSA C10 250.
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Re: M1 jetting question

Postby zxrmad » Sat Jun 25, 2016 9:13 pm

I took the bike for a ride the other day. It revs fairly cleanly when sittling in neutral but when riding it won't rev over about 7k. I'm guessing it's rich in the main jets due to removing the emissions gear? Next time I'm home from work I'll pull the carbs again and open them up to see what jetting they have
Current bikes... '93 ZXR750R M1, '95 ZXR750 L3, '95 ZXR750 track bike, '96 Bimota sb6, '99 Bimota db4, '08 Honda VTX1800, '94 Honda CB250, '00 Honda XR200, CBR400rr race bike, '49 BSA C10 250.
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Re: M1 jetting question

Postby zxrmad » Sun Jun 26, 2016 8:10 pm

I pulled the carbs again this arvo, stripped tham and recorded all the settings/ jets etc. The size of the jets, needles and some of the settings were completely different to what the stock settings in the manual for the M are, which confused me a little as these were brand new never used carbs. Then I checked my manual for '91/ '92 K model and the settings match the K model. So these are new K model carbs. Not so bad as they are identical except for some jets and settings.

Main jets in the K carbs are way smaller (138) than the M carbs (190/ 200). Which makes sense to me now as when I rode it, I got a few more revs out of it when I pulled the choke on. It didn't make sense to me att He time because I thought it would be way rich after removing the emissions gear but the fact that the choke made a slight improvement would indicate that it was lean.

I have a couple different sets of main jets, so will have a play.


Cheers,
Brian
Last edited by zxrmad on Mon Jun 27, 2016 8:42 pm, edited 1 time in total.
Current bikes... '93 ZXR750R M1, '95 ZXR750 L3, '95 ZXR750 track bike, '96 Bimota sb6, '99 Bimota db4, '08 Honda VTX1800, '94 Honda CB250, '00 Honda XR200, CBR400rr race bike, '49 BSA C10 250.
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Re: M1 jetting question

Postby greenman43 » Mon Jun 27, 2016 5:51 pm

From memory the kit setup requires 152s, not sure how anything much bigger than that will work.

Cheers,
Brian
07 ZX10R track 09 ZX6R road/track 93 ZXR750 race 89 GPZ900 project
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Do not walk in front of me, for I may not be following
Do not walk alongside me, for the path may be narrow
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Re: M1 jetting question

Postby zxrmad » Mon Jun 27, 2016 9:27 pm

greenman43 wrote:From memory the kit setup requires 152s, not sure how anything much bigger than that will work.

Cheers,
Brian


I'm guessing that is with kit type enclosed airbox? Still trying to get my head around the jetting, there's so many different settings that I've seen depending on type of airbox etc.

I changed the mains to 155's today and took it for a ride. It now revs to about 9k and then bogs so is a bit better. Again, it seems slightly better with the choke partly on which still indicates to me that it is still lean. I don't have the manual with me at the moment but from memory the stock settings for M model with stock airbox and air filter is 190/ 180 mains. Not sure how much of a difference removing the emissions crap makes. I think I have a set of 180 mains in my stash so might give them a try when I get home.

Cheers
Brian
Current bikes... '93 ZXR750R M1, '95 ZXR750 L3, '95 ZXR750 track bike, '96 Bimota sb6, '99 Bimota db4, '08 Honda VTX1800, '94 Honda CB250, '00 Honda XR200, CBR400rr race bike, '49 BSA C10 250.
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Re: M1 jetting question

Postby greenman43 » Mon Jun 27, 2016 9:56 pm

It is, and with a fully-worked engine and no filtration. IIRC, standard was 190/200 for mains.

I don't recall the emissions crap making any difference to jetting.

Cheers,
Brian
07 ZX10R track 09 ZX6R road/track 93 ZXR750 race 89 GPZ900 project
Do not walk behind me, for I may not be leading
Do not walk in front of me, for I may not be following
Do not walk alongside me, for the path may be narrow
Just piss off and leave me alone
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Re: M1 jetting question

Postby zxrmad » Tue Jun 28, 2016 7:46 pm

Cool, I'll give the 180's a go on the weekend. Do you know why the factory staggered the stock jetting (190, 200, 200, 190)? Is it something to do with the inside 2 cylinders running leaner due to the higher operating temp? They also do it with the needles and needle clip position
Current bikes... '93 ZXR750R M1, '95 ZXR750 L3, '95 ZXR750 track bike, '96 Bimota sb6, '99 Bimota db4, '08 Honda VTX1800, '94 Honda CB250, '00 Honda XR200, CBR400rr race bike, '49 BSA C10 250.
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Re: M1 jetting question

Postby greenman43 » Tue Jun 28, 2016 9:26 pm

Yes, I believe so. The kit settings all ignore that aspect, so safe to say it was negligible.
07 ZX10R track 09 ZX6R road/track 93 ZXR750 race 89 GPZ900 project
Do not walk behind me, for I may not be leading
Do not walk in front of me, for I may not be following
Do not walk alongside me, for the path may be narrow
Just piss off and leave me alone
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Re: M1 jetting question

Postby ZXRPI » Wed Jun 29, 2016 12:21 pm

Hey Brian (ZXRMAD),

Like Brian (greenman43) I haven't experienced any jetting difference with or without the emissions crap on various ZXR engines over the years.

I think 180's will get you closer to the happy running mark.

As a reference, I am currently running 175 mains and 48 pilot with kit needle on the richest clip. These settings are on a fully worked engine running OEM M1 airbox with BMC filter.

Breaking down at higher revs is not always an indication of jetting with the FCRs on ZXRs in my experience. On my current set-up, I spent a long, long, long time getting the fuelling spot on. Actually, getting jetting close wasn't too bad. Was actually getting the float bowl venting / pressure right that was a pain. I had problems with revs breaking down at high rpm. In the end, spent 13 odd hours on the dyno at PTR (Phil Tainton) playing with airbox pressure and finding optimal pressure. The guys at PTR even set-up a MOTEC ECU and put pressure sensors in the airbox and ram air tube to get it right. In the end, for my settings we've actually got the bowl vent running into the ram air intake about 3 - 4 inches in from fairing. Achieved a very stable AF ratio, no breakdown / leaning out at high rpm and good HP! Just took ages to get it spot on!

Not trying to scare you!! Just thought you'd be interested. :D
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Re: M1 jetting question

Postby zxrmad » Wed Jun 29, 2016 8:02 pm

Hi Dominic. I sent you a PM the other day but not sure if you got it? it stayed in the outbox for a while.

I just have the float bowl vents plumbed back into the LH side of the airbox at the moment.

I'm still learning about tuning these carbs and most of it is guess work for me to be honest. I hope to be able to get it running good enough to ride and then hopefully get it on a dyno some time for the fine tuning. I've never had a bike (or anything for that matter) on a dyno before but I can imagine it will be a time consuming exercise removing carbs to change jets/ settings and then go again. Time = money I guess, so if I can get it close by mucking around with it myself I'll hopefully save some time and might even learn something in the process.

The needles, main air jets and pilot air jets are different between the K carbs and the M carbs, so I don't know if that is going to be an issue for me? Not sure if I should buy the correct needles and air jets as per the M manual or not?

I'll chuck the 180 mains in on Friday and see how it goes anyway.

Cheers,
Brian
Current bikes... '93 ZXR750R M1, '95 ZXR750 L3, '95 ZXR750 track bike, '96 Bimota sb6, '99 Bimota db4, '08 Honda VTX1800, '94 Honda CB250, '00 Honda XR200, CBR400rr race bike, '49 BSA C10 250.
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