Keihin diagnostics

Simon · May 15, 2008

OK chaps!

Having been thoroughly pleased with the performance of my dellorto for so many years

, I came across an FCR some time ago (this is the FCR not the FCR MX so no start circuit). First things first, I put the Lineaweaver jet kit in.

Now on test ride it is far from linear in its delivery. I get a surge of power which then tails off. Let me give an example. Cruising down the driveway with throttle just off closed it trundles along just fine, then suddenly, without throttle turn, it takes off. Out on the road, I'll twist the throttle from low revs, initially I get nothing, then wham - in 1st - 3rd this is mono wheel wham btw :wink: - which then becomes gentler as we go. The carb just isn't connected to my wrist.

It's all fairly low down in the throttle range this happens

Another thing is a slight missfire cruising at about 60-70mph.

Currently it is a bog stock 03 650 engine with oem enduro exhaust system.

I've ridden plenty of 650s with the fcr so I know what they should feel like when right.

Right now I'm tempted to go back to the dellorto because it has worked so well for me over the years. As it stands the fcr just isn't very ridable.

My initial thought is to step up the idle by a size and maybe go up to a 160 main from the 150. It's the surge I want to get rid of first.

What's the thoughts.....?

All the best,
Simon

sparks · May 15, 2008

Simon said:
OK chaps!

Having been thoroughly pleased with the performance of my dellorto for so many years , I came across an FCR some time ago (this is the FCR not the FCR MX so no start circuit). First things first, I put the Lineaweaver jet kit in.

Now on test ride it is far from linear in its delivery. I get a surge of power which then tails off. Let me give an example. Cruising down the driveway with throttle just off closed it trundles along just fine, then suddenly, without throttle turn, it takes off. Out on the road, I'll twist the throttle from low revs, initially I get nothing, then wham - in 1st - 3rd this is mono wheel wham btw :wink: - which then becomes gentler as we go. The carb just isn't connected to my wrist.

It's all fairly low down in the throttle range this happens

Another thing is a slight missfire cruising at about 60-70mph.

Currently it is a bog stock 03 650 engine with oem enduro exhaust system.

I've ridden plenty of 650s with the fcr so I know what they should feel like when right.

Right now I'm tempted to go back to the dellorto because it has worked so well for me over the years. As it stands the fcr just isn't very ridable.

My initial thought is to step up the idle by a size and maybe go up to a 160 main from the 150. It's the surge I want to get rid of first.

What's the thoughts.....?

All the best,
Simon

Hi Simon,

The first thing you can do Simon is get rid of that #48 pilot jet mega rich, you want to be down to a #38 at least, and just under 0.5 of a turn on the PAS.

Regards

Sparks.

Taffy · May 15, 2008

RE: Re: Keihin diagnostics

you sound rich low down with an MJ that's bordering on lean i suspect. you are so rich that the bike missfires. i suspect your lineaweaver needle is in clip 3/4 when it should be in 1.

agree with sparks on the PJ but you may want to start conservatively at 40. suspect it'll be a sod to start so i would keep the APJ fitted. when it's needed it makes a difference and when it keeps squirting after it's needed it doesn't reduce performance so keep it for your cold starts.

regards

Taffy

Simon · May 15, 2008

RE: Re: Keihin diagnostics

Thanks chaps,

I'm already on the 38 pilot but 1.5-2 turns out on the PAS.

Hmmmm, I think you might be right on the needle.

I'll try some adjustments - clearly things aren't too far out.

Cheers,
Simon

sparks · May 15, 2008

Re: RE: Re: Keihin diagnostics

Simon said:
Thanks chaps,

I'm already on the 38 pilot but 1.5-2 turns out on the PAS.

Hmmmm, I think you might be right on the needle.

I'll try some adjustments - clearly things aren't too far out.

Cheers,
Simon

Bear in mind Simon the Lineaweaver needle is rich on the straight as well, the one he sent me measured thinner in diameter than the R straight, the straight on my needle now is an S.
If you run a 40 PJ 0.5 of a turn on the PAS.

I think it has been said before that the gas in the states is not quite as volatile as over here in Europe, and it has some sort of Oxygen induced into it this could be why over in the states they seem to be using excessive jet sizes which when used over here in Europe the engines run as rich as hell.
Just a theory.

Regards

Sparks.

BelgiqueBasterd · May 15, 2008

Simon said:
OK chaps!

Having been thoroughly pleased with the performance of my dellorto for so many years , I came across an FCR some time ago (this is the FCR not the FCR MX so no start circuit). First things first, I put the Lineaweaver jet kit in.

Now on test ride it is far from linear in its delivery. I get a surge of power which then tails off. Let me give an example. Cruising down the driveway with throttle just off closed it trundles along just fine, then suddenly, without throttle turn, it takes off. Out on the road, I'll twist the throttle from low revs, initially I get nothing, then wham - in 1st - 3rd this is mono wheel wham btw :wink: - which then becomes gentler as we go. The carb just isn't connected to my wrist.

It's all fairly low down in the throttle range this happens

Another thing is a slight missfire cruising at about 60-70mph.

Currently it is a bog stock 03 650 engine with oem enduro exhaust system.

I've ridden plenty of 650s with the fcr so I know what they should feel like when right.

Right now I'm tempted to go back to the dellorto because it has worked so well for me over the years. As it stands the fcr just isn't very ridable.

My initial thought is to step up the idle by a size and maybe go up to a 160 main from the 150. It's the surge I want to get rid of first.

What's the thoughts.....?

All the best,
Simon

Had the same symptoms when I put the lineaweaver needle in my 2002 with a FCR. I have now sent it to a Husaberg specialist, who will put it on the Dyno, I'll keep you guys informed how it turns out.

Simon · May 16, 2008

Re: RE: Re: Keihin diagnostics

sparks said:
Bear in mind Simon the Lineaweaver needle is rich on the straight as well, the one he sent me measured thinner in diameter than the R straight, the straight on my needle now is an S.
If you run a 40 PJ 0.5 of a turn on the PAS.

I think it has been said before that the gas in the states is not quite as volatile as over here in Europe, and it has some sort of Oxygen induced into it this could be why over in the states they seem to be using excessive jet sizes which when used over here in Europe the engines run as rich as hell.
Just a theory.

Regards

Sparks.

Cheers sparks.

Simon

Simon · May 16, 2008

BelgiqueBasterd said:
Had the same symptoms when I put the lineaweaver needle in my 2002 with a FCR. I have now sent it to a Husaberg specialist, who will put it on the Dyno, I'll keep you guys informed how it turns out.

You need to bear in mind that mine has had at least 20 odd dyno runs already. The problem is that the usual inertia dyno is not going to give you the real world answers. The air/fuel ratio measurement equipment just doesn't have the response times on a power run and therefore you'll need to run it under load at steady state through the whole range. Both time consuming and costly. Your normal inertia sweep test, or basic 10 minute brake test won't cut it in this instance.

However, I now have a data logging system that attaches to the bike to do "dyno" testing in the real world, which I'm hoping should turn out to be rather interesting.

All the best,
Simon

BelgiqueBasterd · May 16, 2008

Simon said:
BelgiqueBasterd said:

Had the same symptoms when I put the lineaweaver needle in my 2002 with a FCR. I have now sent it to a Husaberg specialist, who will put it on the Dyno, I'll keep you guys informed how it turns out.

Click to expand...

You need to bear in mind that mine has had at least 20 odd dyno runs already. The problem is that the usual inertia dyno is not going to give you the real world answers. The air/fuel ratio measurement equipment just doesn't have the response times on a power run and therefore you'll need to run it under load at steady state through the whole range. Both time consuming and costly. Your normal inertia sweep test, or basic 10 minute brake test won't cut it in this instance.

However, I now have a data logging system that attaches to the bike to do "dyno" testing in the real world, which I'm hoping should turn out to be rather interesting.

All the best,
Simon

Interesting Info, didn't know that!

This guy doesn't do it just for the money, he does it because he likes tuning engines. Last Husa he did he did 17 runs on it before he tought it was ok. So it definately won't be a rush job.

So if I understand you correctly your bike has had 20 runs with this carb setup and you still have such a poor result?

Simon · May 16, 2008

BelgiqueBasterd said:
So if I understand you correctly your bike has had 20 runs with this carb setup and you still have such a poor result?

Yes. The dyno results show that the carburettor is just about right on its setup. The a/f ratio reading were useless so we had to go by the graphs themselves.

In real terms it is not such a poor result, it's just something that the dyno (inertia) is not sensitive enough to pick up. The dyno has alway just been a tool and to be fair we weren't using the dyno trying to set up the jetting, we were testing several prototype exhaust systems and silencers I've designed - but of course, to do that well enough the carb had to be in the ball park.

Cheers,
Simon

Simon · May 31, 2008

RE: Re: Keihin diagnostics

Well, I'm slowly getting there on this one and I think the results so far are going to surprise you a bit.

I now have a 40 idle, mixture screw 2.5 turns out (I trust it is actually a mixture screw not an air screw), needle in 4th from top and 160 main. I'm almost on the verge of putting in a 42 pilot or raising the needle a clip position or two.

The other thing is, after all the nonsense, it still doesn't start as easy as my trusty dellorto!!!!!

All the best,
Simon

sparks · May 31, 2008

Re: RE: Re: Keihin diagnostics

Simon said:
Well, I'm slowly getting there on this one and I think the results so far are going to surprise you a bit.

I now have a 40 idle, mixture screw 2.5 turns out (I trust it is actually a mixture screw not an air screw), needle in 4th from top and 160 main. I'm almost on the verge of putting in a 42 pilot or raising the needle a clip position or two.

The other thing is, after all the nonsense, it still doesn't start as easy as my trusty dellorto!!!!!

All the best,
Simon

Strooth Simon 2 1/2 turns out on the FMS, this generally donates that the PJ is to small but I'm on 1 1/4 on the FMS and a #38PJ.
Starts first kick every time well nearly sometimes two.

Regards

Sparks.

Simon · Jun 1, 2008

RE: Re: RE: Re: Keihin diagnostics

Yeah, it's surprising. Even more so is that I've had an afternoon going step by step up through the pilot jets, 40, 42, 45, 48 and even a 50 and step by step on the mixture screw on each jet.

I've ended up on a 48 pilot with screw .5 turns out (yes fourty eight - not a typo). 160 main and the Lineaweaver needle on 6th from top. Exhaust system is the standard oem enduro.

I have to say the Lineaweaver needle gives a wicked pull through the rev range.

Cheers,
Simon

sparks · Jun 3, 2008

Re: RE: Re: RE: Re: Keihin diagnostics

Simon said:
Yeah, it's surprising. Even more so is that I've had an afternoon going step by step up through the pilot jets, 40, 42, 45, 48 and even a 50 and step by step on the mixture screw on each jet.

I've ended up on a 48 pilot with screw .5 turns out (yes fourty eight - not a typo). 160 main and the Lineaweaver needle on 6th from top. Exhaust system is the standard oem enduro.

I have to say the Lineaweaver needle gives a wicked pull through the rev range.

Cheers,
Simon

Simon the .5 of a turn out on the FMS is telling you something, the PJ is way to rich.

Regards

Sparks.

Simon · Jun 3, 2008

Re: RE: Re: RE: Re: Keihin diagnostics

sparks said:
Simon the .5 of a turn out on the FMS is telling you something, the PJ is way to rich.

Regards

Sparks.

On this occasion I've got to beg to differ sparks. Normally I'd agree with you but in this instance I'm more than 2.5 turns out on the 45 jet - actually it doesn't even run right at 3.5 turns out which tells me it's wanting a larger jet more than it's wanting a smaller jet on the 48 at .5 turns - if that makes sense.

I've got to go with my experience and that's what it's telling me. With anything less, it's impossible to balance the idle mixture and idle speed adjustment. At this setting it solves all my problems.

Clearly, for some reason it just isn't getting the necessary vacuum signal to run adequately on anything else.

All the best,
Simon

kzoo · Jun 3, 2008

RE: Re: RE: Re: RE: Re: Keihin diagnostics

Are you using an after-market aluminum fuel screw? This sounds somewhat familiar to what I was experiencing when fitting an FCR to my '03. I could not run the bike on any jet unless the fuel screw (FS) was out 3 turns or something like that... I had been using an after-market aluminum FS and the metering needle was not machined correctly (too large). When I put the OEM brass FS in all my troubles disappeared. I've since searched for the like problem on another bike forum and it seems to be somewhat common with the aluminum units.

sparks · Jun 3, 2008

Re: RE: Re: RE: Re: Keihin diagnostics

Simon said:
sparks said:

Simon the .5 of a turn out on the FMS is telling you something, the PJ is way to rich.

Regards

Sparks.

Click to expand...

On this occasion I've got to beg to differ sparks. Normally I'd agree with you but in this instance I'm more than 2.5 turns out on the 45 jet - actually it doesn't even run right at 3.5 turns out which tells me it's wanting a larger jet more than it's wanting a smaller jet on the 48 at .5 turns - if that makes sense.

I've got to go with my experience and that's what it's telling me. With anything less, it's impossible to balance the idle mixture and idle speed adjustment. At this setting it solves all my problems.

Clearly, for some reason it just isn't getting the necessary vacuum signal to run adequately on anything else.

All the best,
Simon

Simon I don't doubt what you are saying or how your engine is running but I think you are chasing your own arse here, I think you have some sort of problem else where, we know all jetting differs from engine to engine and location to location but I think yours are a bit to the extreme.
I know exactly how mine would run on your set up S***e, I think if I was you I would investigate a bit further there something quite not right some where.

What PAJ are you running the standard #100 or the adjustable one?.

Regards

Sparks.

Simon · Jun 5, 2008

RE: Re: RE: Re: RE: Re: Keihin diagnostics

The PAJ is an oem item (from an oem jet kit) and it is adjustable and I have played around with it.

The thing is I'm not chasing my arse here, sparks - I've found settings that work and they work well, it's not necessarily a sign of a problem. I think looking further is simply going to be chasing my tail.

If there were still problems in the behaviour when running it would be a different matter but where it is it starts well and runs well whatever the temperature (engine and ambient) and it has good characteristics over the entire throttle range. And dyno testing has now confirmed this.

Interestingly there is another pattern that confirms things are OK. The more restrictive an exhaust system (I have more than a dozen with various flow characteristics) I put on the bike the larger the pilot jet required which tells me it is a clear function of the intake vacuum not necessarily a "problem" with the carb.

Thanks for your input though - it's helpful to keep questioning where one is at!

All the best,
Simon

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