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Discussion Starter #1
Hello i have a 2004 KFX 700 im wanting to do a 800 bigbore problem im having is im getting many diffrent solutions but i just want a reliable 800 motor doin all the work myself just need guidence on parts to get so please someone iout there could throw together a good list for me with site links i would much appreceate it thank you love my kfx
 

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First off, are you buying the cylinders already bored out? What kit are you going with?

I have an 800 and I did all the engine work myself.

Mine is a 11.5:1 compression FourStrokeTech kit, I like the lower compression because it helps keep it reliable, but many people on this site run reliable 800's with a higher compression (i.e 13.1:1)

Degrease and powerwash your engine FIRST, you'll appreciate this step later on

Here's what I did: Not in this order..

1) Disassemble your top end and lay out all of your parts in order on a table. Label the Front/Rear rocker covers and heads.

2) (Optional) Baggy up your bolts and label the bags as to where the bolts go that way assembly goes smoothly.

3) If you have a 2004 if it necessary to do the rocker modification so that your rockers don't seize up and cause engine failure.

800 Kits can be purchased from a few different sources such as

www.bigkevs.com/index.htm (Sells AMR, after midnight racing)

www.fourstroketech.net (FST)

Fundy makes some reliable kits, not sure of his website but someone will post it.
 

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Fudy is one of the supporting venders.
 

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I noticed I spelled Fudy, must of been thinking FUDY DUD!!
 

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I noticed I spelled Fudy, must of been thinking FUDY DUD!!
I'm sure Ray will appreciate the plug for Fudy Power Sports :lol::lol::lol:.

I have an FPS 730 so I can't really speak for the 800's, but thus far I have not heard of any relibility issues with Ray's Kits. And they are plenty fast.
 

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I noticed I spelled Fudy, must of been thinking FUDY DUD!!
I'm sure Ray will appreciate the plug for Fudy Power Sports :lol::lol::lol:.

I have an FPS 730 so I can't really speak for the 800's, but thus far I have not heard of any relibility issues with Ray's Kits. And they are plenty fast.

No, I was thinking of you when I posted:lol: I have nothing againsted FPS...
 

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Discussion Starter #9
Ive been looking at the fundy perfomance kit ive actually been wondering ive gotten the run around on this my plan was to have my cylinders sleeved with the sleeves in the kit from fundy is that going to work is there any problems that i shoud whatch out for doing that ? as well perfomance wise are the stock carbs big enough? lol sry and does anybody make an intake kit?
 

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You' be well off using a Fundy kit with the sleeves he uses.

Seems like I hear a lot about 800's having a lot of head gasket issues due to the sleeves being incorrectly installed. I haven't had any such issues.

As far as your intake goes, I suggest that as you get exhaust you also do the 12-hole modification which is drilling 12 1" holes in your air box LID, 3 on each side (none on the top)

I use stock carbs on my 800 with no problem. I love the reliability and snappiness of the stock carbs, but running stock carbs is power limiting.
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You might want to consider a 730 kit, which is a simple overbore of your cylinders +2mm to an84mm piston. You can get some great power out of a 730 kit. Stock carbs will work better and you have no sleeve issues
 

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Discussion Starter #11
THanks for all the feedback its nice to get some good answers thank you as well if i were to go with the 800 would you have any suggestions on a machine shop that would correctly install those sleeves or did you do the machining yourself?
 

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THanks for all the feedback its nice to get some good answers thank you as well if i were to go with the 800 would you have any suggestions on a machine shop that would correctly install those sleeves or did you do the machining yourself?
After you select your kit maker I would recommend you have them do the machine work / sleeving. They will have your new pistons and can get everything matched up at their shop and ship it to you ready to bolt up.
 

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Pretty much now, there haven't been any reliability issues with the 800 kits. All the bugs have been worked out on the standard stuff. If you start doing stupid things and experimenting, that is a different story.

Any of the builders suggested can get you a kit together. Just make sure you upgrade everything that the builder suggests/says must be done to run their kit. Don't half a$$ or allow someone to tell you its ok to half a$$ the build.

Update the rockers to be safe. You will also need to put in an oil return for a catch can. The can may not be needed, Normally just putting in the lines helps prevent it from blowing oil.


You will achieve greater gains with the smaller bore kits for less money vs an 800 kit.. You can wake the 800 up a lot if you upgrade exhaust and carbs etc..

You save like 6-1000 in the build cost by not having to sleeve the cylinders.
 
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