Hey guys, was just wondering what your opinion on a good, can't say "the best", 727 big bore, for the raptor, also what is the best piston to get, with reliability and also not having to run full-on race gas.
Thx, Lewis

 

Craycraft 727 is probably the best in my opinion. But you can build your own, and still get a pretty mean combo. That is what I did with my 686, and the yamaha dealership swears that it pulls harder than a trinity 727, but i have my doubts, could be though. If you build your own just make sure you get the head done by someone that knows what they are doing. But if I were doing it I would start by sending the jug to LA sleeve and have it resleaved and bored to 105mm, then I would send the head to craycraft racing, and have it ported, polished, valve job, and oversized valves with kibbelwhite valve springs. Then I would use a JE 12.5 to 1 comp. piston. Then with that big of a motor I would also put a carrilo rod in it just to be safe. Your stock carbs won't work with that motor so you would need a set of 35mm FCR carbs, but if it were me I would spend the extra money and just buy the KMS fuel injection kit, because it will be much easier, and probably more reliable. If you have any other questions just let me know I have done quite a bit of research into these motors, so i may be able to answer your questions.

 

Craycraft Racing's Low Compression Cruiser (LCC). It's a 10.5:1 piston with either Craycraft's cam (high rpm, needs a Dyna ignition), Hotcams Stage 2, or Megacycle X-4. It's an ultra-reliable pump gas motor that doesn't mind a shot of nitrous every now and then if you need the speed. Craycraft offeres a couple of different porting packages including a sub-contract to the best in the industry, Tim Barker. Craycraft has switched from Carillo rods to Barker's rods, CrMo or Ti. This is a solid build that runs stronger than 99% of the Raptors on the face of the planet. Craycraft can mod your stock carbs if money is tight but you'll get the best performance from a set of 39mm FCRs.

There are other shops that build good big bores but I have no experience with them. I have a lot of experience with Craycraft and have always been treated right. Performance, price, turn-around time, reliability, and customer service are all top shelf.

 

Lou, it is a little rough you to call some of these builders to talk about what you are going to do with your bike and what your going get for the money you spend.

I would look at your budget for the overall bike.

How can I make my bike real fast for a set amount of dollars.

I've seen 727's pull well over 65 hp with the right port job, X4 cam, dual exhuast, stock ignition and modded stock carbs.

If your bike chassis isn't ready for the extra hp (swingarm etc.) your not going to be any faster with add ons like $1100.00 carbs or $400.00 ignition.

The stock Raptor connecting rod is weak.

 

Okay thanks for the advice, as for the chassis coyote, (swingarm) I do not have a new one yet, was looking at a +2 or +3 though, but with a 12:1 would I need to run race fuel or is 97-100 octane okay?
Thanks, Lewis

 

Lou, I run a plus 4" swing arm on mine. It is a little short for all out drag racing/hill shooting because my bike puts out 70hp.

I mostly dune with it (in Glamis) and while I'm out will run Oldsmobile hill (if we are near it) a few times then resume the duning.

My bike is 11 to 1 and runs fine on premium unleaded mixed with race gas. It loves fresh VP Red though.

12 to 1 may seem like just one more point in the compression ratio but will by way more sensitive to pre-ignition. Just not sure what grade of fuel is readily available to you in Canada?

A 10.5 to 1 piston as mentioned earlier in the thread is a great piston and runs on pump gas. There would have to be a pretty compelling reason not to consider it.

The Hot rod ideal and these forums should be about keeping it simple, reliable (available) and as inexpensive possible.

 

i know of several 727's that make over 70hp and a screamer that makes 80hp. A big piston like a 730 will rev slow if your not carefull, a 686/690 are going to rev faster than the bigger bores.

 

Are you folks having any head gasket sealing issues with the 105mm bore? Do you need to modify the head's squish chamber with the big bore kits?

DV

 

Whats this about a KMS Fuel Injection system??

 

i would take a craycraft over anything