what compression to use on 440 kit?

[brandonpeake]

alright ive decided im sending my motor to duncan, what compression would u reccomend , ive decided to go with the mid to top cam
i want reliability ,but using race gas does not bother me
i dont want to be worring about it blowing up everytime i ride
input please

[RED121572]

Since your using a high end cam, the more compression you have, the better your bottom end will be. Ive got an 12.5.1 piston in mine with a low end cam. I couldnt be more happier with mine. It falls a bit short on the high end, but it pulls like a freight train off the bottom.

Good luck with your choice!!

RED

[brandonpeake]

so the higher compression will workl better with the top end to mid cam? is the higher compression not a reliability issue?a

[Texan32]

since you are wanting a top end cam, that means that you are going to be running in the upper RPM range. So, the higher comp. piston will assist in getting the rev's up quicker. 12.5:1 shouldn't be a real reliability issue, as long as you take care of her (ample oil changes, possibably aux oil cooler, not bouncing off the rev limiter all the time....). With that high of compression, you will probably have to run at least pump/race gas mix, if not straight race gas.

[brandonpeake]

okay let me add some more info too it , its maily going to be a mx bike but i will go play ride on it also
so its not going to be just a race bike,
is the setup i mentiond above best for this?

[brandonpeake]

also , im new to the ex so ive never seen the oil cooler who makes them? i was planning on runnig an oversized um racing oil reservoir,but never seen the cooler , please give more info
is an 8 plate clutch necessary for the 440?

[Texan32]

ok first let me ask you this. Have you thought about your SUSPENSION?! The EX motor is more than capable of taking you around an MX track quickly. Replacing the stock suspension will make you faster than any motor mod you can think of or do. FACT. The very first thing i did to my EX was throw on a DMC Alien exhaust. About a year later, i upgraded my shocks to Elka Race shocks. As much as i love my pipe, if i had to do it over, i would buy the shock 10 times before i bought the exhaust. Upgrading the suspension makes such a difference, once you have riden on it, you will NEVER want to ride on stock pogo's again!

Ok, off my soapbox....since you don't mind the price of race gas, yes it is a great set-up. Duncan has been building motors for a number of years. They will hook you up.

Oil cooler - it is an auxilirary cooler that you place inline with the exhisting lines. FST (Four Stroke Tech) makes supposedly one of the best.

Oversize reservior - (personally) waste of money. Aux. cooler offers MUCH better bang for the buck. The Ex is a dry sump system. Noone has yet shown (me) any hard evidence of its benifites...i.e. lower oil temps....In fact, i think it was Duncan that was testing a built Z-400 WITHOUT an oil reservoir!

8 plate clutch - i don't think it is DEFINATELY NECESSARY. But, it will definately strengthen THE weakest link in the drivetrain. The hinsen basket is much stronger than stock. And, the added plate helps reasure that you are getting all the grunt to the back tires.

[brandonpeake]

i got tcs dual rate with rezzies with comp and rebound im sending my rear shock to get rebuilt by tcs
so yeah i agree with u and your soap box , aftermarket shocks are the only way to go

2nd, anyone know if fst has a website or how to get in touch with them
so would you go with 12.5 to 1 comp?, next the qucik change clutch cover, has anyone sed the xr400 one yet, how much of an ordeal will this be ,if its doable whats the part # to it so i can pick one up
thanks for all the info

[Texan32]

good to hear about the suspension:cool:

I don't remeber if he had one or not. He has a spot in the back of dirt wheels.

Clutch cover - there are several here that have this. The XR400 cover fits like a glove...but...
1. You have to have a plug made to close up the hole that the kick starter shaft sticks out of.
2. Because of the size of the clutch basket assy., you are forced to run a Hinsen cover.

sorry, but thats all i know about the cover.....

Since you are going big bore w/ higher comp., you might want to look into the head bolt/stud kit. I don't have any specific info, but i know it is a set of thicker diameter head stud/bolt/nuts. Less likely to blow gaskets.

[brandonpeake]

the duncan kit im looking at comes with it
but i just got off the phone with lrd and for 1350 i can get the 440 kit and exhaust but its just like a bore and cam basically,said puts out about hi 30s hp
but the " half" kits i would think is where u get into trouble, but they said its low enough heat to not need the hardened rockers b/c they dont port it, but i thought u got most of your hp out of the port?

[Texan32]

i don't know what all is included in either builder's kits. Both are VERY respectable. You will find ample number of supporters for both. Its really up to you...it is YOUR money.

there is a misunderstanding here. Hard facing the rockers has nothing to do with porting. The materail and "lumpyness" of the cam determine weither or not you need hardened rockers. The only way to know is to ask the cam maker.

porting....there are dozens of shops out there that can port a head. But, you should look for someone that can bench flow the head. If you port too big or at the wrong angles, you can do more harm than good. Seeing as how you are looking at a decient motor rebuild, the port job is not a MUST, but it will absolutely compliment the work already being done.

carb...have you thought about a larger carb? the FCR 39 would be an excellent fuel pump:D

[brandonpeake]

i was under the impression that due to the extra heat from the port job is one reason the rockers needed hardening,
lrd told me if i had anyhting besides the kit they installed even a rev box it would be like sitting on a bomb, just seems like living on the edge to me
but they are very reputable and honest so maybe he was trying to save my motor
i guess its up to whether i got an extra grand from between the 2