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SlammedRanger

400ex stroker (440ex) build thread

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4 hours ago, shadetree said:

looks a tad on lean side too me ?.

It was only running 10 minutes at most. The plug very end was just starting to change colors. And like i said it was just idle and a few revs. Zero riding on this plug. Obveously its impossible to read a plug with that little run time and zero ride time. But the fact that it changed at all makes me think im either still alittle rich on pilot jet or its spot on. Its still acting rich. Idle dropping after revs but i dont know until i go for a ride. Idle and rev doesnt tell me enough.

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Still needs a smaller sprocket on the rear axle too. Not because it needs any more speed in any gear, but because overly high gearing is required to smooth violent wheelspin while exiting corners and following upshifts to improve overall lap times. The motor produces an excessive amount of torque per pound of bike/rider which presents a big problem. The wheel/tire combo can be dampened in those excessive torque cases by extending/prolonging reaction moments. To achieve that you either must increase the rubber surface area contacting the ground (larger tires) or gear it high enough that reaction moment shock (causes instantaneous wheelspin) where the tire meets the track is minimized.

 

It feels really weird to work on that... it feels like you are slowing the vehicle down and feels counterproductive. But a lap timer reveals the truth. The vehicle is a lot easier to drive once its optimized as well. My buddy has a saying that we used an awful lot, especially during qualifying on wet tracks and while running in the short 4 car dash races: "Slow down, go faster". Try it, practice it.... your lap timer and clipboard will like it. 🙂

 

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31 minutes ago, retro said:

Still needs a smaller sprocket on the rear axle too. Not because it needs any more speed in any gear, but because overly high gearing is required to smooth violent wheelspin while exiting corners and following upshifts to improve overall lap times. The motor produces an excessive amount of torque per pound of bike/rider which presents a big problem. The wheel/tire combo can be dampened in those excessive torque cases by extending/prolonging reaction moments. To achieve that you either must increase the rubber surface area contacting the ground (larger tires) or gear it high enough that reaction moment shock (causes instantaneous wheelspin) where the tire meets the track is minimized.

 

It feels really weird to work on that... it feels like you are slowing the vehicle down and feels counterproductive. But a lap timer reveals the truth. The vehicle is a lot easier to drive once its optimized as well. My buddy has a saying that we used an awful lot, especially during qualifying on wet tracks and while running in the short 4 car dash races: "Slow down, go faster". Try it, practice it.... your lap timer and clipboard will like it. 🙂

 

Im looking at a case protector that can fit a 15 tooth front sprocket.

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I'm not experienced in four stroke wheelers tuning but I am an expert with high performance two strokes and small engines. My thoughts on it idling funny after revving tells me it is a needle or main problem. Here's my logic. When the engine is dropping revs after blipping the throttle it still has the mixture of the blip influencing the overall mixture.  If it is off this will affect the idle speed until the engine turns over enough times to equalize the idle mixture. The is more pronounced in two strokes

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8 hours ago, Misterclean said:

I'm not experienced in four stroke wheelers tuning but I am an expert with high performance two strokes and small engines. My thoughts on it idling funny after revving tells me it is a needle or main problem. Here's my logic. When the engine is dropping revs after blipping the throttle it still has the mixture of the blip influencing the overall mixture.  If it is off this will affect the idle speed until the engine turns over enough times to equalize the idle mixture. The is more pronounced in two strokes

I would agree but it doesnt matter how much throttle i give it. Even if i just tap the throttle slightly it causes the idle to drop and sometimes it will drop enough to stall. It actually seems like the higher revs and even up to the limiter if it has to drop further it stays running atleast. But still drops i would say roughly 300 or 400 rpms.

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I can tell im getting closer with the pilot jet because it does atleast stall when i turn the mixture all the way in. But it does still run for about 15 or 20 seconds after the mixture is all the way closed. So more research is saying it should stall at or slightly before its all the way closed. So the 42 pilot jet is on its way. Its crazy to me how small a pilot jet this thing is asking for. But im just taking it as my motor is pulling some serious vacuum and able to pull alot more fuel out of a smaller jet. I really dont suspect the needle is an issue at all. It revs super fast and the throttle response is really good. And im running the ncvq needle that everyone raves about. I will at some point be trying to raise the clip to the mid point and i know that will probably make me have to put a bigger main jet in. But if its anything like the 416 it will make it stumble when revving and confirm one clip down from mid is where it needs to stay.

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I agree with you @SlammedRanger, you're getting close with the pilot. The Hi-comp piston dome stuffing the volume in the top of the chamber combined with the large bore, long stroke and short rod L/R ratio (piston acceleration away from TDC is high) increase the signal strength at the jet, which makes the jet more responsive and efficient. The jet flows a greater volume of fuel in response to high abrupt pressure changes. Thats the main reason why the motor now requires smaller jets throughout. Its gonna be a responsive torque monster once you get it dialed in on all three enrichment levels.

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One thing to concider here thE FCR also has a Slow air jet you might want to look into replacing that with a 95. I'm pretty sure stock is 100. Also the needle taper should be a NCVQ. You can also.try a NCYR or NCVT. Honestly you can chase your tail all day thinking that you have it right when the easiest thing to do is have someone who tunes then everyday handle your problem. When you start adding performance you start running into tuning problems. Take my bike for instance. I sent my carb off to Jet-lab and had Danny go through it and taper bore it to 43.5mm . I got it back bolt on ready except for the idle and a slight 1/8th turn on the fuel screw. And she ran like a scalded dog. 188 main, 45 slow, 100 slow air 42 leak, NCVQ needle center clip. Now... when I went and tuned I ended up with a Drilled 205 main and clip to the bottom of the needle. That's the difference in tuning on a dyno and bench tuning. I picked up 4.85hp with the first  jet change.  Moral of this story.... swallow your pride and have a professional help. That's what they are there for. 💪💪theres the proof.... I cant show my final numbers🤭🤭

20191011_144801.jpg

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8 minutes ago, TRX2FiveO said:

I cant show my final numbers🤭🤭

 

Aww come on, just the torque figure...? HP means nothing you can keep that one.🧐 😛

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The air jets have me kinda stumped. I dont really understand the symptoms of what a wrong one causes. There is no tuning places around me that i trust. So unless i buy my own dyno which im not doing lol. Its a seat of the pants dyno and lots of trial and error. One change at a time. I am happy to see your jetting is down near where mine is. I was really concerned i was gunna end up way lean and burning this thing up. But it has never gotten even close to hot. My oil temp dip stick hasnt gone above 160 since my 416 build. So i know it was rich. Which i know can do just as much damage as lean so i havent really done any long rides. And i changed my oil after the first ride where it was puffing black smoke from being so rich. Didnt want to take any chance the oil was fuel contaminated.

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I know nothing about FCR circuits but I got confidence in ya, you'll get it right.

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54 minutes ago, retro said:

 

Aww come on, just the torque figure...? HP means nothing you can keep that one.🧐 😛

!.... let's just say she is almost in the 40s... ALMOST. 

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11 minutes ago, SlammedRanger said:

The air jets have me kinda stumped. I dont really understand the symptoms of what a wrong one causes. There is no tuning places around me that i trust. So unless i buy my own dyno which im not doing lol. Its a seat of the pants dyno and lots of trial and error. One change at a time. I am happy to see your jetting is down near where mine is. I was really concerned i was gunna end up way lean and burning this thing up. But it has never gotten even close to hot. My oil temp dip stick hasnt gone above 160 since my 416 build. So i know it was rich. Which i know can do just as much damage as lean so i havent really done any long rides. And i changed my oil after the first ride where it was puffing black smoke from being so rich. Didnt want to take any chance the oil was fuel contaminated.

Pull the air jet and tell me what the number is

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1 minute ago, TRX2FiveO said:

!.... let's just say she is almost in the 40s... ALMOST.

 

Thats outstanding!!!!

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Just get you one of these and you'll never have to jet again😬😂  maybe not that big😂😂😂 that would drown you. 

received_2411746889154394.jpeg

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20 minutes ago, TRX2FiveO said:

Pull the air jet and tell me what the number is

Can do! I will text it to you bro! Thanks!

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***Update***

 

After talking to moose for a while on the phone today i think we may have figured out why my quad is so rich on the pilot cercuit. The pilot air jet in my fcr is way way rich. And as usual moose is the man and gunna send me the air jet he thinks i will need. What is and has been in my carb since i got it was a 70. He is sending me a 100. I still dont know how my 416 ran so good on a 50 pilot jet and a 70 air jet. It should have been insanely rich at idle. Guess its a good thing i was on the main and needle 90% of the time! LoL

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***Update***

 

100 air jet in and she idles so smooth. No hunting just steady. I can rev it at idle and it revs and the idle doesnt drop or stall when coming down! I have the 45 pilot jet in still and mixture at 2 turns. Cant wait to take it for a ride. But the idle issues are atleast a thing of the past. Thanks again moose! You da man!

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35 minutes ago, SlammedRanger said:

***Update***

 

100 air jet in and she idles so smooth. No hunting just steady. I can rev it at idle and it revs and the idle doesnt drop or stall when coming down! I have the 45 pilot jet in still and mixture at 2 turns. Cant wait to take it for a ride. But the idle issues are atleast a thing of the passed. Thanks again moose! You da man!

You're  welcome buddy. Glad to help

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***Update***

 

The 100 slow air jet made alot of positive difference. No more idle issues. And it starts up instantly with zero issue warm or cold. And i say warm because it never got even close to hot. This is hands down the coldest running 400ex i have ever come in contact with. It has to be pig rich somewhere. I did find the rev limiter a few times. And @retro was 1000% correct on gearing. This thing just will not hook up with the 18s. I found this out first hand as i was doing a full 360 at about 20 or 30 mph across my dads back yard. Hands down scariest thing i have ever done. Ive done full 360s at speed on frozen ground but never on dry dirt/grass before. I am going to be ordering a glann innovations case saver that will work with a 15 tooth front sprocket. The 14/36 isnt enough gear. 15/39 here i come.

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Glad to hear you haver er dialled in! 

 

It can sometimes be a real pain jetting after major modifications!!!! But the pay offs are huge once dialled in! 

 

Congrats!

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1 hour ago, SlammedRanger said:

The 14/36 isnt enough gear. 15/39 here i come.

 

Is that a typo? Try 15/35... or get some more rubber on the ground with taller/wider tires. 😅

 

Your motor is running cooler than you're accustomed to because its way more efficient in nearly every measurable category. VE is probably approaching 114% - 115% at the torque peak. BSFC (Combustion efficiency) is way up and piston speed near 70-75 degrees ATDC is high. You haven't rode it much yet to form an opinion, but fuel economy should be noticeably good too. What you are experiencing is normal and expected when you design and build a proper torque monster. Built motors run hot because they are NOT built to be efficient, which means they're way down on torque too.

 

Once you get your carb set up right its gonna produce even more torque and it'll run a few degrees cooler than it does now!

 

Gear it way higher than you feel that you should and it'll be just right for producing your fastest lap times.

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No not a type-o just gunna go one change at a time. I cant run a 35 on the rear. Sprocket protector wont allow it. And i will tell you fuel milage is horrible. My tank was full when i started riding. I would say i was on it a total of 25 to 30 minutes tops. I was below a half a tank when i got home probably closer to 1/4. Shes rich somewhere. Im kinda thinking its needle position. Or maybe needle itself at this point. Cuz when i was spinning around i was on the limiter. And i was catching it out of the corners when i was feeling the wheel spin. So im thinking the main is where it needs to be. It did seem alittle flat in the mid throttle range. Throttle response was crisp and off idle it was a monster. I did crack the throttle in 3rd gear at speed and had zero issue maintaining a power wheelie. So we are getting close. But i bet i pull the plug and its dark. I can also now drop the break-in oil and filter and put in my amsoil. Fingers crossed theres no glitter! LoL

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