Main Jet Size FCR 41 '93 M900?

[JimE]

Looking for a little advice on selecting the main jets for my new FCR 41's. Here's the story.....

I just got the kit from CA Cycleworks and it went in with what appears to be the usual amount of fiddling. The stock carbs had been running rich and lurchy due to what is most certainly very worn needle jets. I had been meaning to replace them but instead waited and got the FCR kit. In the meantime I had replaced the exhaust with a RoadRacing underbike setup. The bike ran pretty rich at idle and partial throttle as you could smell the unburnt fuel, and lean on mid to open throttle as I could feel some heat and smell a little oil after higher speed running. So in went the FCR's. I did everything but open the airbox lid (which had no snorkels to begin with when I got it) and went for a test ride. The bike popped a bit and felt lean but otherwise okay. Better off the line for sure. So then I cut the airbox lid and did some running at a standstill to test. The bike now belches flame out the exhaust and after about a minute or less of mid throttle running the pipes were glowing cherry red. Way, way, way too lean. Totally unrideable. I'm ruling out issues like fuel pump, timing, etc, etc because the bike ran pretty well before. I just can't see these things changing. That and the most significant difference was opening the airbox and just running the bike on the sidestand. I had told CA Cycleworks on order that I had this type of exhaust and my intent to put some Vee Two cams in there. Either they didn't pay attention or don't know what I'm talking about. Looks like I'll have to fix this myself.

So the question is this: how much richer should I start with? I've got to get the main sorted first. I'm thinking at least 3 sizes like a 162 (came with 155). I just don't want to buy a bunch of different jets I'll never use. Anybody have any advice on where to start? Any input would be appreciated!

-Jim

[koko64]

G'day Jim E

I think your 'Guestimation' is about right. The open air box has a significant effect. I am running an open air box and Termi slip-ons and run 165 main jets. Note that I also have advanced cams, porting and hi comp pistons. 162 or 165 mains wouldn't be a bad place to start. With an open air box you may also have to raise the needle a notch (at least you can drop it again at no extra cost).

Consider a dyno test after installing bigger mains and be prepared to spend some time being systematic with recording jetting changes and testing each one. Check out Patrick Burns tuning guide link on Chris' Cal Cycleworks site re FCRs.

Take your time and don't beat yourself up if you buy jets, test them and then change them. It happens and you will have them to help out a buddy (that's what I tell myself). The main jets are dirt cheap in the States compared to Australia.

Enjoy your FCRs, they are a beautiful thing.

Cheers

[greenmonster]

The RR exhaust is also quite restrictive in original shape.
A good idea is to open them and take all out (I mean everything!).
They will be LOUD but work better.

[JimE]

Well I ordered some new jets from CA Cycleworks. I asked Chris to put something together for me that might point me in the right direction. No idea what it's going to cost. Not really important I would have paid it up front if I'd known I might have to do it. Jets are cheap. What is important to me is getting him to do so felt like pulling teeth. While I agree with most of what he had to say the attitude of "put it on a trailer and take it to a tuner" and "those are the settings that work" regardless of my bikes described behavior left me with a bad feeling. While I agree that paddock tuning is relatively useless and real tuning happens on the track the fact is this: if it won't run in the paddock it won't run on the track. The response I got when I called asking for advice was defensive, argumentative, and just short of being called an idiot. I finally beat them into selling me some jets to try.

I can understand some of this as they probably get a lot of mechanical dummies doing this but I'm not one of them. I ran an RS125 in AFM and USGPRU for six years. Won two AFM 4 hour endurances in the 250 class (on a 125), took 5th in the west coast nationals in 2003, and have a bunch of plastic doo dads in my office called trophies. Since I did all my own tuning and ran Keihin carbs I may know how to jet something. Just maybe. Also since I have a BSME, sailed in the US Merchant Marine as an Engineering Officer, worked as semiconductor equipment engineer, and now own a company installing and servicing generators I may be a decent wrench. Just maybe. So I found myself rather offended at the treatment I received when I called for some help and to spend some more money with them.

At any rate time to move on. In the future I shall keep in mind that anything else I buy from them will come with the same level of support. When I get new jets I'll start by paddock tuning with the main until it stops belching and overheating, then start the track testing. A 165 will go in first and we shall see. I'll post the results when I get to major milestones in the hopes that somebody else won't get quite as frustrated. I have a feeling I'll have new settings for all of it. When I feel comfortable it'll be down to the dyno for some runs and perhaps some EGA time as well. When I get those I'll post up as well.

In the meantime keep the suggestions coming if you have them. Advice is free and worth every penny.

Cheers

[koko64]

Well I ordered some new jets from CA Cycleworks. I asked Chris to put something together for me that might point me in the right direction. No idea what it's going to cost. Not really important I would have paid it up front if I'd known I might have to do it. Jets are cheap. What is important to me is getting him to do so felt like pulling teeth. While I agree with most of what he had to say the attitude of "put it on a trailer and take it to a tuner" and "those are the settings that work" regardless of my bikes described behavior left me with a bad feeling. While I agree that paddock tuning is relatively useless and real tuning happens on the track the fact is this: if it won't run in the paddock it won't run on the track. The response I got when I called asking for advice was defensive, argumentative, and just short of being called an idiot. I finally beat them into selling me some jets to try.

I can understand some of this as they probably get a lot of mechanical dummies doing this but I'm not one of them. I ran an RS125 in AFM and USGPRU for six years. Won two AFM 4 hour endurances in the 250 class (on a 125), took 5th in the west coast nationals in 2003, and have a bunch of plastic doo dads in my office called trophies. Since I did all my own tuning and ran Keihin carbs I may know how to jet something. Just maybe. Also since I have a BSME, sailed in the US Merchant Marine as an Engineering Officer, worked as semiconductor equipment engineer, and now own a company installing and servicing generators I may be a decent wrench. Just maybe. So I found myself rather offended at the treatment I received when I called for some help and to spend some more money with them.

At any rate time to move on. In the future I shall keep in mind that anything else I buy from them will come with the same level of support. When I get new jets I'll start by paddock tuning with the main until it stops belching and overheating, then start the track testing. A 165 will go in first and we shall see. I'll post the results when I get to major milestones in the hopes that somebody else won't get quite as frustrated. I have a feeling I'll have new settings for all of it. When I feel comfortable it'll be down to the dyno for some runs and perhaps some EGA time as well. When I get those I'll post up as well.

In the meantime keep the suggestions coming if you have them. Advice is free and worth every penny.

Cheers

Sorry to hear that Jim E.

I ordered 165 mains with my FCRs knowing I'd need them, they cost $1-50 each from the same store. My experience of Cal Cycleworks was very different as I had the pleasure of dealing with the charming Candice.

My previous experience with some FCR 39s on a Superlight with nearly the same mods determined my starting point. With your substantial experience you'll have those carbs tuned soon, no worries (if you can tune a two stroke you'll have no problem with a Monster)!

I'm finding the 60 slow jets very rich so I'm mucking around at the other end of the rev range.

I'll be watching with interest and comparing notes.

Cheers

[krista]

Hi Jim,

I apologize that I wasn't able to earn your respect with my own experience. After all, I was only an Electronics Technician enlisted guy in the Navy, only have a BSEE (magna cum laude), and only raced WSMC for 3 years (was class champion in the final year).

Admittedly, when people calling me for advice argue with me and discount my experience and suggestions, my patience goes thin. At no time did you even offer me the chance to actually help you. You don't want to even try to begin the process of finding where the fueling problems are on your bike.  I have been installing and selling the FCRs going back to about 1995 -- and on my own personal 1992 900ss had the identical condition of putting on the carbs and they coughed and spit.

To say that the support I lent you is lacking is an absolute lie. And your post bashing my company is uncalled for and shows how you have lost touch with reality from your time spent aggrandizing yourself. No one else in the motorcycle industry would have suffered your condescending attitude for an hour on the phone and still actually delivered you parts that best meet your requirements. And for less than retail, at that. I am personally committed to the products we sell and helping our customers.

I wish you the best of luck sorting out your carbs. Once you have ridden your bike with them and can relay back to me the throttle position of where your bike is acting lean, I'll gladly discuss your current jetting and offer my suggestion on where to go next. Had you actually allowed the bike to move under its own power, you could have helped me not send you an excess of tuning options.

You won though ... you pulled my teeth and got all the jets and needles, but I wasn't able to pull yours -- you kept arguing that you want to tune your bike for operating on its side stand.

Yaaay.
Chris
:|

Well I ordered some new jets from CA Cycleworks. I asked Chris to put something together for me that might point me in the right direction. No idea what it's going to cost. Not really important I would have paid it up front if I'd known I might have to do it. Jets are cheap. What is important to me is getting him to do so felt like pulling teeth. While I agree with most of what he had to say the attitude of "put it on a trailer and take it to a tuner" and "those are the settings that work" regardless of my bikes described behavior left me with a bad feeling. While I agree that paddock tuning is relatively useless and real tuning happens on the track the fact is this: if it won't run in the paddock it won't run on the track. The response I got when I called asking for advice was defensive, argumentative, and just short of being called an idiot. I finally beat them into selling me some jets to try.

I can understand some of this as they probably get a lot of mechanical dummies doing this but I'm not one of them. I ran an RS125 in AFM and USGPRU for six years. Won two AFM 4 hour endurances in the 250 class (on a 125), took 5th in the west coast nationals in 2003, and have a bunch of plastic doo dads in my office called trophies. Since I did all my own tuning and ran Keihin carbs I may know how to jet something. Just maybe. Also since I have a BSME, sailed in the US Merchant Marine as an Engineering Officer, worked as semiconductor equipment engineer, and now own a company installing and servicing generators I may be a decent wrench. Just maybe. So I found myself rather offended at the treatment I received when I called for some help and to spend some more money with them.

At any rate time to move on. In the future I shall keep in mind that anything else I buy from them will come with the same level of support. When I get new jets I'll start by paddock tuning with the main until it stops belching and overheating, then start the track testing. A 165 will go in first and we shall see. I'll post the results when I get to major milestones in the hopes that somebody else won't get quite as frustrated. I have a feeling I'll have new settings for all of it. When I feel comfortable it'll be down to the dyno for some runs and perhaps some EGA time as well. When I get those I'll post up as well.

In the meantime keep the suggestions coming if you have them. Advice is free and worth every penny.

Cheers

[koko64]

Jim E

A hard lead draws a heavy counter.

Cal Cycleworks gave me the best service I have yet experienced from a bike shop. All the quoted base settings were perfect (including the float levels). (They have the e-mails from me to prove it).

That aside, I'm curious as to how your bike goes with the bigger main jets. I have heard (not verified) that the fuel quality or composition may vary a great deal between countries affecting jetting. I already had a workable baseline for my motor.

It's interesting to note that the Dynojet kits for CV carbs run up to 165ish mains (DJ175) for open air boxes ,yet the Factory Pro kits run 155 mains for the same mod. Of course these are baseline settings.

The FCR instructions included say that the kits are jetted for stock bikes. Chris sends them with 155s as a baseline. From his substantial experience he would have had to settle for something close to the needs of most people out of the box, not an easy undertaking.

Good luck

[Speeddog]

Keep in mind that Mikuni and Keihin main jets won't necessarily flow the same, even if they have the same numbers.

Mikuni has several different main jet configurations, some with different numbering schemes.

[koko64]

Very true SD
I probably could have made myself more clear. Damn, do you know how many times I edited that post?! 

My point was to show how two companies with great expertise were offering different jetting ranges for the same open air box mod. (I was also sure to take into account Dynojets numbering system). I was trying to draw something from that.

[greenmonster]

It's interesting to note that the Dynojet kits for CV carbs run up to 165ish mains (DJ175) for open air boxes ,yet the Factory Pro kits run 155 mains for the same mod.

Mikuni & DJ are different even if they have the same size number on them.
DJ measures hole diameter & M flow rate: http://roadstarclinic.com/content/view/61/96/
So DJ 165 is close to M 155.

[koko64]

Mikuni & DJ are different even if they have the same size number on them.
DJ measures hole diameter & M flow rate: http://roadstarclinic.com/content/view/61/96/
So DJ 165 is close to M 155.

 [laugh]G'day Greenmonster
You are absolutely right. Lets talk Mikuni sizes and take the conversion as read.
Dynojet were saying go 165 and Factory Pro were saying 155 for open airbox on their jet kits.
I will never edit a magazine
I sent you a pm.
Cheers

[greenmonster]

You`re welcome!
Nice to be a wise ass sometimes....

[koko64]

Misunderstood by all, Kwai Chang Caine wanders into the wilderness playing his flute...