700fi Motor Build - Unleashed UTV

KJSmith84 · #31 (**permalink**) 07-06-2009, 01:47 PM

Quote: Originally Posted by Big Slick

Ya KJ that would be awesome. I live in litchfield park. I would also like to drive someone that has a 734 kit done. Have you raced a rzr on flat ground or in the dunes?

no i havnt - ok as soon as its back together I will shoot you a pm to cruise over.

**07fj** · #32 (**permalink**) 07-06-2009, 01:51 PM

Quote: Originally Posted by KJSmith84

Big Bore kits

Advantages:
Relatively easy
Changing just the cylinder and piston is easier than splitting the cases and installing a stroker crankshaft.
Cheaper than a crank, but not by much.

Disadvantages:
Head is not designed for that diameter cylinder.
Too large bore results in incomplete combustion
Too large bore reduces cooling jacket.
Larger piston adds stress to rod and crank.
Excessive vibration from heavier piston. Still need to remove crank to rebalance for heavier piston assembly. But if you do all that work, you might as well use a stroker crank.

Stroker Cranks

Advantages:
Stock Piston sizes are cheaper to replace and easier to get.
More torque
Better traction
Easier to control
Complete combustion – using head designed for this bore.
Longer stroke breathes “deeper” while valves are open.
Generally, better power than bore kits

Disadvantages:
If done poorly, can result in vibration
Very large stroke may require case modifications
Somewhat more expensive than big-bore kits.
Few companies can do it properly.

I am glad your machine is performing well, but what you describe here are at the most, generalities and opinions.

KJSmith84 · #33 (**permalink**) 07-06-2009, 01:57 PM

Quote: Originally Posted by 07fj

I am glad your machine is performing well, but what you describe here are at the most, generalities and opinions.

just pulled that from the internet from a engine builders site-wanst even utv related just general engine building observations

rhinoyfz · #34 (**permalink**) 07-06-2009, 02:04 PM

I have had the hot rods +5 crank for 9 months and no problems. recommend it. lots of torque. even had stock exhaust on it for 5 months. duned it with 4 200+ pound dudes on a night ride with no problems. it was like duneing a stock 700 with just me, and i dont have the cam. definitly get the chromoly stud kit though, did blow a head gasket. the casting flaws in these mass produced engines suck, you can see it with your naked eye on the mating surfaces.

mac rhino · #35 (**permalink**) 07-06-2009, 04:18 PM

Stroke gives torque and torque gives acceleration hp gives top speed. I have had an 8mm stroke with a big bore for a year with no problems. Hits 67mph on flat ground fairly easy. Stroking the motor was well worth it. It is nice others are doing it and having a good ride

zkriegel · #36 (**permalink**) 07-06-2009, 05:33 PM

Where did you end up with the clutch? (spring color/weight)

**Pgreg** · #37 (**permalink**) 07-06-2009, 11:09 PM

I am in SD in Mission Bay RV park until the 12th. I will post up some pics and pricing info when I get back. I do have to say when when went on the Glamis night run in June I was very impressed with how well Kyle's car ran with how little we really did to it. It went up China Wall faster than my Teryx did. We had issues along the way but learned what to do for a reliable motor. The first time out with Kyle's car we ran it hard in the summer heat and had no problems. Our basic package will be priced right and get results. Thanks to Kyle again for the write up and the patience.

For those asking about clutch set up we ran a gold secondary spring and 16g weights with our slidder kit and I think Kyle bought a sheave from another vendor before coming to us. The clutch is not finished yet I have some more ideas.

shanksyamaha · #38 (**permalink**) 07-06-2009, 11:31 PM

How does price to HP compare to doing a rotax motor?? Seams the rotax guys are getting alot of power, with potential to mod further... I know the rotax swap is expensive but would it be a better duner with the twin??

**Pgreg** · #39 (**permalink**) 07-06-2009, 11:40 PM

Quote: Originally Posted by shanksyamaha

How does price to HP compare to doing a rotax motor?? Seams the rotax guys are getting alot of power, with potential to mod further... I know the rotax swap is expensive but would it be a better duner with the twin??

I don't have exact numbers yet but probably 75% less than a Rotax mod.

shanksyamaha · #40 (**permalink**) 07-06-2009, 11:49 PM

Quote: Originally Posted by Pgreg

Quote: Originally Posted by shanksyamaha

How does price to HP compare to doing a rotax motor?? Seams the rotax guys are getting alot of power, with potential to mod further... I know the rotax swap is expensive but would it be a better duner with the twin??

I don't have exact numbers yet but probably 75% less than a Rotax mod.

Well thats definately significant!! I don't think the rotax motor will give you 75% more hp than a built 700fi.

dixie chopper · #41 (**permalink**) 07-07-2009, 06:54 AM

Subscribed.......... Great info guys.

michaeltom401 · #42 (**permalink**) 07-07-2009, 09:35 AM

[quote=Pgreg;351221]

Quote: Originally Posted by shanksyamaha

How does price to HP compare to doing a rotax motor?? Seams the rotax guys are getting alot of power, with potential to mod further... I know the rotax swap is expensive but would it be a better duner with the twin??

The rotax swap is going to cost more but is it faster? There are several opinions on that but just the rotax swap alone, with no motor work and bolt-on modifications (exhaust, clutch tuning, etc...) is not going to be quicker on flat level ground than this mod based on his numbers. Once you start to climb comp hill, china wall, etc.. the rotax will win. A well tuned and running Rotax climbs faster with less work than even my 760 Weller motor which puts out about 60 hp on the dyno. That twin is hard to beat in the torque category. In a drag race I would chose the 700fi mod, well running 686, 720 & 760 motors. Add a 840 kit to the rotax it will make it more interesting but still the rhino motor will be as fast or faster on the flats but will lose in a hill climb.

**Brian B** · #43 (**permalink**) 07-07-2009, 09:46 AM

Good to see people making decent power out of the 700's! Great work guys!

How much torque do built Rhino engines make?

**1FAST06** · #44 (**permalink**) 07-07-2009, 10:05 AM

Quote: Originally Posted by shanksyamaha

How does price to HP compare to doing a rotax motor?? Seams the rotax guys are getting alot of power, with potential to mod further... I know the rotax swap is expensive but would it be a better duner with the twin??

I would still stay with the upgrade to your stock rhino motor. I think that a rotax build is alittle over priced.

michaeltom401 · #45 (**permalink**) 07-07-2009, 10:24 AM

Quote: Originally Posted by Brian B

How much torque do built Rhino engines make?

Personally I don't know how much torque a rotax makes. I have witness and ridden with several rotax rhinos and I know that the torque on a Rotax is greater than even my Rhino. You see how much easier and faster the Rotax climbs huge hills which is proof enough for me. Are they quicker on flat ground, NO. Only a Teryx with built motors climb faster. I have a bronco clutch on mine and that does make a huge difference when drag racing on flat surfaces but until someone puts a bronco clutch on a Rotax Rhino I guess we will have to speculate.

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