sman217

I'm sorry.. but Yes... FCR jetting question...

19 posts in this topic

Just picked up my fcr for my 400s converted SM. Purchased from keihin-fcr.com. Jetting is 160 main 45 pilot emn needle, 3rd clip, as per the website. I also have a powerbomb header, powercore 4 slip on, and the usual 3x3. Carb was a PAIN to get on as I'm sure you all know, but it's on. Bike fired up, idles great, and blipping the throttle sounded mean! 

 

That said, i feel The bikes top end is lacking; something is not right. All is good up until about 3/4's to full throttle. In the upper rev range, it's even more noticeable. The bike is only able to do 87 on its 15/44 gearing, and I know it should be able to do a bit more than that. The bike sort of Boggs, or kind of pulsy at WOT; it almost feels stronger at 3/4's throttle. 

 

Ive posted in the DRZ Facebook page and lots said I should run a bigger main.... I questioned that. 160 main is what many say is right on, if not, a tad rich...

 

i took my air filter off and also airbox cover and drove it, and performance was worse. Less torque and less power. I'm pulling the plug right now to analyze what it looks like as well. 

 

Others suggested fuel screw adjustment, but I was under the impression the fuel screw revolved around pilot circuit. My bike idles perfect, and starts great. Also has pretty good kick in torque at 1/2 throttle, so I'm a bit confused. 

 

Any advice?

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To use a plug reading you'll need to find an open road and hold it at WOT for a mile or so and then hit the kill switch and pull in the clutch at the same time . You want to freeze the plug condition as it was at WOT . Coming to a stop and idling ect... without the "plug chop" and all your reading is idle mixture. Start with a new or clean plug.

 

For what it's worth , I have a 170 main in my FCR41 with same exhaust , Uni filter and 3x3.

 

.

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15 minutes ago, ohiodrz400sm said:

How old is that plug?

Old; my guess is maybe an oem plug. I've never changed it. 

 

2 minutes ago, jjktmrider said:

To use a plug reading you'll need to find an open road and hold it at WOT for a mile or so and then hit the kill switch and pull in the clutch at the same time . You want to freeze the plug condition as it was at WOT . Coming to a stop and idling ect... without the "plug chop" and all your reading is idle mixture. Start with a new or clean plug.

 

For what it's worth , I have a 170 main in my FCR41 with same exhaust , Uni filter and 3x3.

 

.

This was right after WOT run. I'm familiar with plug testing!

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I'd start with a new plug. Did you go beyond 3*3 or add any extra holes on your airbox?
Main jets are cheap and can be changed in minutes. I would buy a 165, 158, and 155 to experiment with.

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Going 1 MJ bigger and trying 1 smaller should tell you pretty quick what you need to know.

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3 hours ago, dspy21 said:

Going 1 MJ bigger and trying 1 smaller should tell you pretty quick what you need to know.

Will be testing this theory out this weekend. Where should I order jets from? I don't want to have to get a whole jet kit; just need two mains. 

 

Thanks to both for your help. 

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Jets R Us.

Pay attention and order genuine Keihin jets.

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+1 on using jets r us. Honestly, shipping ($7) is gonna cost more than a handful of jets themselves so don't do what I did and just order several. I ended up buying several needles as well from them but if the mid range is strong on your bike might not want to bother experimenting with that

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2 hours ago, dspy21 said:

+1 on using jets r us. Honestly, shipping ($7) is gonna cost more than a handful of jets themselves so don't do what I did and just order several. I ended up buying several needles as well from them but if the mid range is strong on your bike might not want to bother experimenting with that

I will do such! Just ordered four or five jets. Followed instructions on their website; do these part numbers look good to you all? Yes, I went oem keihin. 

IMG_0628.PNG

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good luck, imho you needed 150 and 155

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1 hour ago, 30x26 said:

good luck, imho you needed 150 and 155

My bikes already running lean; why would you endorse a 150 or 155?

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didn't memorize the part numbers but as long as you navigated the page clicking fcrmx to where you find the jets/add to cart they are the right ones.

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You can't read a 4 stroke plug like a 2 stroke. They will also run cleanly over a wide range of adjustment. I have tried every jet from 142 to 170 and it ran cleanly with every one. Too rich will not rev out. Even at 15:1 air fuel (142 main) it will scream like no tomorrow.

Experience says you should be in the 150 range rather than 160.

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1 hour ago, ohiodrz400sm said:

You can't read a 4 stroke plug like a 2 stroke. They will also run cleanly over a wide range of adjustment. I have tried every jet from 142 to 170 and it ran cleanly with every one. Too rich will not rev out. Even at 15:1 air fuel (142 main) it will scream like no tomorrow.

Experience says you should be in the 150 range rather than 160.

Very odd. Given my mods, every post I read in thumpertalk, and even burned suggestions, pointed at 160 main. I ordered a 158 but I'll order a 150 just for you bud!

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Very odd. Given my mods, every post I read in thumpertalk, and even burned suggestions, pointed at 160 main. I ordered a 158 but I'll order a 150 just for you bud!

Not necessarily a 150 but in that range. I bet a dollar it runs best with a 155
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1 minute ago, ohiodrz400sm said:


Not necessarily a 150 but in that range. I bet a dollar it runs best with a 155

I ordered a 158; if she runs better with that, then I'll go get me a 155! Besides jets r us, could I pick up a jet or two at the stealership? The fcr is such a common carb, I'd be amazed if they didn't have jets....

 

also, I don't know if this contradicts the whole lean / rich arguement, but I ran the bike without the airbox cover on, and took the filter off the bike and it ran a little worse; less torque, still hesitating/mild bucking at WOT in high rev range. This is why people on the Facebook DRZ page reccomended richer main. Some also reccomended toying with needle clip position. 

 

My bike is 70 miles away from me during the week; as I attend college away from my garage. Friday I'll be back tinkering with it, and I'll see what jets are in it for sure, and where the clip is located on needle. According to keihin-fcr, I got a 160 main. Many other with nearly same mods had run 160 mains and said it ran like a "scalded ape" so, it's just odd. I also want to order a 41 tooth rear sprocket for my sumo wheels; I hate the 44. If anyone wants to trade; buy it, it's yours. 

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I ordered a 158; if she runs better with that, then I'll go get me a 155! Besides jets r us, could I pick up a jet or two at the stealership? The fcr is such a common carb, I'd be amazed if they didn't have jets....
 
also, I don't know if this contradicts the whole lean / rich arguement, but I ran the bike without the airbox cover on, and took the filter off the bike and it ran a little worse; less torque, still hesitating/mild bucking at WOT in high rev range. This is why people on the Facebook DRZ page reccomended richer main. Some also reccomended toying with needle clip position. 
 
My bike is 70 miles away from me during the week; as I attend college away from my garage. Friday I'll be back tinkering with it, and I'll see what jets are in it for sure, and where the clip is located on needle. According to keihin-fcr, I got a 160 main. Many other with nearly same mods had run 160 mains and said it ran like a "scalded ape" so, it's just odd. I also want to order a 41 tooth rear sprocket for my sumo wheels; I hate the 44. If anyone wants to trade; buy it, it's yours. 

Each bike is unique. It's possible it wants richer but I doubt it. Not unless it's sucking air or the float level is really low.

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