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Discussion Starter · #1 ·
This Winter I plan to tear into my 1999 Honda 400ex... Its loosing compression and power... My question is.. What do you think of the 44cc big bore kit.. I've heard that they make your motor run extremely hot..

I have the 16cc bore kit on my 2002 Honda 400ex..It's running 12:1 Compression and 110 octane fuel...
What Compression do the 44 kits run??

I'm just looking around maybe for more power than the 16cc..

I am going to be starting racing flat track again come spring time so this is going to be my back up race bike...
I would like to run the 44cc kit but I'm worried that my motors going to run hot and I am going to run into more problems..

Let me know what you think..
Thanks
 

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SlammedRanger is the guy you want to talk to about BB kit pros & cons and what it takes to keep them together. FYI... Methanol motors will run a lot cooler than gas motors... is there an open fuel unlimited class..? :)
 

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Are you running stock cam? If so you should upgrade the cam so you don't have to run such a high octane. If I were you I'd just bore to a 426ex.

I attached calculations I ran on dynamic compression ratio for the stock cam and hot cam stage 2.
 

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The reason I asked ic3man5, is because PipeMax provides (almost?) identical figures for DCR vs Octane for gasoline fueled motors. I used to do it the old fashioned way, but long math calcs makes my head hurt... software might've saved us a few innocent brain cells, I hope. :)

 

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I would suggest staying away from the 440 kit. UNLESS you want to drop alot of money in cooling mods and other supporting modifications. The 416 is the safe big bore. The 426 can be just as safe if you purchase a sleeve from LA sleeve and have the jug bored for the bigger sleeve. No matter what bore you go with you will need bigger and stronger head studs. Snure Interlocking can hook that up. To make a 440 reliable IMO at the minimum you will need a 2nd oil cooler, mount them both in your aluminum air shrouds, oversized oil tank, and a spal fan either on both oil coolers or blowing on the engine through the head fins. You will need the 440 sleeve put in a bored out jug. Gt thunder(Snure Interlocking) head studs. Crf450 timing chain, and an aftermarket clutch of some kind to put that power to the wheels. If you can get the cylinder o-ringed that would ve even better but not 100% necessary. You can see why i said it would get very expensive very fast lol. My .02
 
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Just a tad bit overkill on the cooling on a 440 there @SlammedRanger. lol If you bore the cylinder and install an 88mm Sleeve be it from LA. Sleeve or Wiseco you can bore that sleeve to fit the 89mm (440 Piston) without any excessive heating concerns. Add an oversized oil tank and a small Fan to the OEM cooler will keep the temps in a very manageable range. Air scoops are also good to have as they direct more air to the engine. 440 kits are very reliable if done properly. No cylinder should be bored pas 87mm the sleeve walls get extremely thin and will not dissipate heat. There is a guy making a 505 kit for the 400ex now. It's a 96mm piston with a +6 stroker crank. The piston is custom made by Carillo (CP) and custom gaskets by Cometic. He is not experiencing any overheating concerns either. The sleeve he uses is made by LA Sleeve also.
Whatever you decide to build just keep in mind all that bottom work will be useless without great head work. ie. shorten guides , lighter spring set, valves and porting.
 

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Just a tad bit overkill on the cooling on a 440 there @SlammedRanger. lol If you bore the cylinder and install an 88mm Sleeve be it from LA. Sleeve or Wiseco you can bore that sleeve to fit the 89mm (440 Piston) without any excessive heating concerns. Add an oversized oil tank and a small Fan to the OEM cooler will keep the temps in a very manageable range. Air scoops are also good to have as they direct more air to the engine. 440 kits are very reliable if done properly. No cylinder should be bored pas 87mm the sleeve walls get extremely thin and will not dissipate heat. There is a guy making a 505 kit for the 400ex now. It's a 96mm piston with a +6 stroker crank. The piston is custom made by Carillo (CP) and custom gaskets by Cometic. He is not experiencing any overheating concerns either. The sleeve he uses is made by LA Sleeve also.
Whatever you decide to build just keep in mind all that bottom work will be useless without great head work. ie. shorten guides , lighter spring set, valves and porting.

Well i havent been known to under do or under think anything haha. I feel like if i was ever to build one for someone i know or do one for myself i would do a hybrid crf450 swap before i would. But if someone forced me i would do everything i mentioned and more. Needless to say there is a reason you never see my quad or anyones i work on broken down on the trail lol. Thank my OCD haha.
 

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Discussion Starter · #9 ·
Are you running stock cam? If so you should upgrade the cam so you don't have to run such a high octane. If I were you I'd just bore to a 426ex.

I attached calculations I ran on dynamic compression ratio for the stock cam and hot cam stage 2.

Nope I'm running a stage 2 hot cam... I ran 93 octane and she didn't like it...ran horrible... when I put the "Magic Blue Juice" in there shes runs like a bat out of hell... I've never heard of the 426 bore....
 

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Discussion Starter · #10 ·
Just a tad bit overkill on the cooling on a 440 there @SlammedRanger. lol If you bore the cylinder and install an 88mm Sleeve be it from LA. Sleeve or Wiseco you can bore that sleeve to fit the 89mm (440 Piston) without any excessive heating concerns. Add an oversized oil tank and a small Fan to the OEM cooler will keep the temps in a very manageable range. Air scoops are also good to have as they direct more air to the engine. 440 kits are very reliable if done properly. No cylinder should be bored pas 87mm the sleeve walls get extremely thin and will not dissipate heat. There is a guy making a 505 kit for the 400ex now. It's a 96mm piston with a +6 stroker crank. The piston is custom made by Carillo (CP) and custom gaskets by Cometic. He is not experiencing any overheating concerns either. The sleeve he uses is made by LA Sleeve also.
Whatever you decide to build just keep in mind all that bottom work will be useless without great head work. ie. shorten guides , lighter spring set, valves and porting.

Well i havent been known to under do or under think anything haha. I feel like if i was ever to build one for someone i know or do one for myself i would do a hybrid crf450 swap before i would. But if someone forced me i would do everything i mentioned and more. Needless to say there is a reason you never see my quad or anyones i work on broken down on the trail lol. Thank my OCD haha.

Thank you guys for all the good info... I haven't even thought of putting a 450 motor on... hmm thats a fantastic idea and seems like less of a headache.... but I have one problem....the class that I am going to run is buy frame.. I have to stay with the 400 chassis but can run up too a 500cc motor.... should I just buy a used parts bike 450 with a running motor... or try and find a used motor... I think buying a whole bike would be nice because then I can have more extra parts
 

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Just a tad bit overkill on the cooling on a 440 there @SlammedRanger. lol If you bore the cylinder and install an 88mm Sleeve be it from LA. Sleeve or Wiseco you can bore that sleeve to fit the 89mm (440 Piston) without any excessive heating concerns. Add an oversized oil tank and a small Fan to the OEM cooler will keep the temps in a very manageable range. Air scoops are also good to have as they direct more air to the engine. 440 kits are very reliable if done properly. No cylinder should be bored pas 87mm the sleeve walls get extremely thin and will not dissipate heat. There is a guy making a 505 kit for the 400ex now. It's a 96mm piston with a +6 stroker crank. The piston is custom made by Carillo (CP) and custom gaskets by Cometic. He is not experiencing any overheating concerns either. The sleeve he uses is made by LA Sleeve also.
Whatever you decide to build just keep in mind all that bottom work will be useless without great head work. ie. shorten guides , lighter spring set, valves and porting.

Well i havent been known to under do or under think anything haha. I feel like if i was ever to build one for someone i know or do one for myself i would do a hybrid crf450 swap before i would. But if someone forced me i would do everything i mentioned and more. Needless to say there is a reason you never see my quad or anyones i work on broken down on the trail lol. Thank my OCD haha.

Thank you guys for all the good info... I haven't even thought of putting a 450 motor on... hmm thats a fantastic idea and seems like less of a headache.... but I have one problem....the class that I am going to run is buy frame.. I have to stay with the 400 chassis but can run up too a 500cc motor.... should I just buy a used parts bike 450 with a running motor... or try and find a used motor... I think buying a whole bike would be nice because then I can have more extra parts
Good luck finding a good running CRF450 engine at a reasonable cost. All the mounts will require fabbing too. Though not impossible and ive seen it done. Its a beast of an engine too

Sent from my LG-US996 using Tapatalk
 

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Discussion Starter · #12 ·
Did a bit of researching and I think I'm just going to do the 44cc big bore kit and the upgraded cooling options lol... people want some crazy money for a 450....
 

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Did a bit of researching and I think I'm just going to do the 44cc big bore kit and the upgraded cooling options lol... people want some crazy money for a 450....
Told Ya... LOL People think those engines are Gold. You will have a fast machine if you get some good head work and upgrade to a FCR carb.
 

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Florida heat, Sugar sand. I have had a 440 kit in my machine for a couple of years now, no issues. I did this for my cooling.
 

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Discussion Starter · #15 ·
Wow that's one gorgeous bike! Its hard to see in the pics but did you just add a second oil cooler?
 

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Thanks, I took the stock cooler and rubber mounted it to one of the scoops, then added a second stock cooler in the other scoop. Seems to help out.
 
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Discussion Starter · #17 ·
I have those air scoops on my Gray 400 and they seemed to help a lot. I notice less heat on my legs when I ride.
 

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Discussion Starter · #18 ·
Florida heat, Sugar sand. I have had a 440 kit in my machine for a couple of years now, no issues. I did this for my cooling.
How do you like those Elka Shocks? Do you race?
 

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The scoops definitely help, now imagine that air pouring over those oil coolers mounted inside them. I also wrap my header which I know is a no no but.......it really helps keep temps down. I dont race much any more but I did for years. Both my boys raced on that bike and other machines at various GNCC races and our state wide FTR racing series since they were very young. Yes indeed! I love my Elkas. Probably one of the top five improvements on my machine. Looks like you have a nice bike as well, modded?
 
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Discussion Starter · #20 ·
The scoops definitely help, now imagine that air pouring over those oil coolers mounted inside them. I also wrap my header which I know is a no no but.......it really helps keep temps down. I dont race much any more but I did for years. Both my boys raced on that bike and other machines at various GNCC races and our state wide FTR racing series since they were very young. Yes indeed! I love my Elkas. Probably one of the top five improvements on my machine. Looks like you have a nice bike as well, modded?
That's so cool that your kids run the GNCC. I used to run the Open class A with my old 1999 honda 300ex. I hurt myself really bad so I decided to quit while I was ahead.

My main baby is a 2003 400ex frame with a 2002 motor. Its got a Wiseco 16cc bore and other goodies. The other stuff is in my Sig. I built it to start flat track racing this upcoming season.

I also still have my old hare scramble bike that I ride the most out of all my bikes. It's the most reliable and never let me down.

I have the Works Suspension shocks on the 400 and they are killer awesome, so incredibly smooth. I've rode a buddies bike that had the elka shocks and they were very smooth.
 
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