PassionRE

Whether they are worth the money or not is a relative statement. The bottom line is that they work and they work very well regardless of the price. Depending on your mods, your porting arrangement, and what your goals are in performance are, in some cases the are almost a neccessity to restore crisp throttle response on motors that are set up for upper mid to high end power curves...Jim

Lian, its not that a hopped up RD400 doesn't have much top-end as much as that the front end is so light under acceleration with the sleeper frame configuration that you would have to have a death wish to stay on the gas fully over 100 mph. With the stock frame set-up you cant steer it under power because it makes so much power the front end isn't even on the ground. You just point it and gas it and hope it stays between the lines...Jim

If you dont deck from the bottom, ported cylinders can be used even if the ex. ports have been raised considerably, but you will have to relieve the combustion chambers for adequate squish clearance with 795 series pistons. If you deck from the bottom approx. .070"-.080" depending on what squish clearance your shooting for, the distance from the top deck to the top of the ex. ports should not be less than 28.3mm. At this spec with a +4 long rod crank ,ex. duration will be 198 degrees. The max considered by most(although I have exceeded this point on certain occasions). Decking from the bottom at the .070-.080 spec advances transfer timing to roughly 114 degrees ATDC, not neccessarely a bad thing although it does affect idle quality. This idle situation is something I'm willing to live with in order to maintain the forced convection cooling characteristics of the piston head and combustion chamber by leaving the piston well within the protection of the bore instead of stuffing it into the combustion chamber with relieved heads..Jim

No case mods needed, definately porting needed if you have a taste for real horsepower. 795 series Wiseco pistons for the long rod motor, cylinder will have to be decked or head mods....I personally prefer decking. If your set-up properly 34 Keihin's with v-force reeds will give crisp throttle response and blistering top-end. Ditch the stock head and run a Noss Machine head.....save yourself problems in advance..Jim

Heres a pic of my original 76' RD400 with just a few mods...haha, and a pic of my wifes fully restored 76' RD200..Jim http://zepher.bikepics.com/pics/yamaha-rd4...pics-080045.jpg http://zepher.bikepics.com/pics/yamaha-rd2...pics-080047.jpg I affectionately refer to my 400 as the "Geeker Sleeper"...will eat up a 600 up to about 100 mph

The basic format originally was the Yamaha R5, the piston port version of a reed valved RD350(air-cooled). Then upgraded to the RD400,(I have a 80 hp RD400) ,and then the RZ350 in the USA with water cooling and power valves. The Banshee is nearly identicle to the RZ motor except for porting, power valves, and tranny upgrades...Europe and Canada had RD series water-cooled versions at the same time the RZ was in production for the US....Jim

Race fuels are used for reliability purpouses almost exclusively. Race fuel has the exact same BTU value as normal gasoline, but deters detonation and hot spots in high compression engines. Justintoxicated, if your referring to what to use in your bike, 110 octane at 50/50 mix with pump fuel for now. And honestly, on your engine that might be a little overkill. but you can just flog the crap out of that engine all day long if jetted properly and be safe. And THAT is what it's all about..well worth the cost...Jim

I'm with Screamin Banshee ,Maxima products are real performers, specifically the 927 Racing Castor...Jim

Banchetta, actually I just shipped a motor for that particular application and goal in mind! One of the board members will be giving us a progress report in the next couple of weeks on how it turned out. Although, I can already tell you that the top end increases with that particular engine will be enhanced bigtime with bigger carbs than he plans on using...but I think he might be leaning torwards a set....we'll see ...Jim

The +4 everyone is talking about is 4mm increased stroke length with 5mm longer rods. It's also available with standard rod length but most everyone prefers the longer rod version. These cranks assembly's are built by Wiesco and are available through many outlets and atv shops for less than $500. Mods to your cylinders and/or head are required to extract full potential in horsepower. The end result is bottom end that simply cant be duplicated by stock cranks and if ported correctly will rev to the moon as well with no lag in any area of the rpm range....Jim

Another thing you must consider is that most of these pipes are developed with basicly stock engines. Different porting arrangements may yield more peak rpm with pipes that normally are not considered great top end pipes. In contrast I have also found that different porting arrangments yield more low-end power with pipes that are not considered great low-end pipes over pipes that are...go figure..It really is rocket science...Jim

Sorry, 18cc domes, I said "chambers" in reference to combustion chambers...Jim

What type of filter set-up are you running? Are you ported? Traditionally cv carburation systems require restriction through the filters and or air box in order for the cv portion of metering to operate properly. ...Jim

H300F, that porting you have works GREAT with 34PJ's and CPI's! Tons of bottom end and a seamless powerband as far as you can stand it. In the future if you want even more, slap a set of 18 chambers in there, run race gas, and call me for a couple of very minor port mods to go absolutely balistic...Jim

The +4 stroker adds big punch down low and if you port it specifically for the +4 long rod crank it makes pretty much solid power from about 1800 rpm all the way through around 11K with a set of CPI's with no lag anywhere. Even without the big bore pistons you cant hit 80hp...big bore stroker?...gee..how much power do you need?...Jim

Justintoxicated!.....decided to drop your load huh?...go with the 33's on your port job...but honestly, get those v-force reeds first ,and if you can only get one of them now,...go for the reeds...your cylinders should be there in a couple of days, and after you get them, keep your hands where we can see them...Jim

A +4 stroker ported correctly is like the difference between a Honda Civic and a 396 SS Chevelle. A drop in +4 without taking in consideration of increased stroke doesn't even scratch the surface of what is available in the horsepower department. As for carbs, on +4's I reccomend 33's as a minimum if ported correctly. If not correctly ported, it doesnt matter, just leave ths stockers on there as your motor h.p output increase will be moderate at best. Go with the 795 series Wisecos for pistons and decking of the cylinder, or head mods will be in order as well. As for power output, with your pipes and mods Ive mentioned 80 h.p. is very achievable.....just depends on how radical you want it...Jim

+4 stroker is a better route.

Oh yeah, David, does my avatar look familiar?...Jim

Biased or not!....ck out David's avatar..have you ever seen billet aluminum look so sexy?...oh yeah, ck out my avatar as well!....Jim

Minkia38, have you run those pipes on any motors running 197+ ex. duration, and if so, at what rpm are they falling off at?..thanks Jim

Unless your planning on porting for all out top-end down the road, PT mids work really well down low and rev as hard as most people care for...just a thought...Jim

Whats your elevation? The carbs will fit your manifolds although they will stretch out a little and eventually you will be forced to upgrade those manifolds. Your reeds are just perfect and will do nothing but make those carbs work their best. I would guess stock pilot ,and around 160-170 on the main for a slightly rich mixture...Jim

How much compression are you running and what fuel? Which pistons are you running at what clearances? Its not uncommon to do this, but I will be willing to bet the next time you do it, if your situation isn't investigated, it will lose the cylinder and wont come back. BenBB has a great section on his webpage for jetting advice...ck it out! Actually, Factory Yamaha road race teams used to set there motors up tight on purpouse, partially seize them, teardown, smooth the seizure marks out, and run them that way, all on purpouse....Jim

PWK stands for PART WITH your KASH. yes, flatslide design....really nice carbs...Jim