Thoughts on pilot 400 cylinders? I also have a few questions about them...

[Shawn]

It has a big sleeve 89mm in side and the top lip of the sleeve is a 102mm I was told it has a cr 500 sleeve

[Pumashine]

A custom pipe is about $500 I believe. Yes you need a balanced crank for an 89mm piston. That is the size my new Saber is. Tractor pulling power is what you will have. But your looking at least $1000 for crank and pipe. Do you know the history or build specs?

[Jerry Hall]

I have not built any 250Rs with 400 Pilot cylinders nor do I think that I could build a lower end for one that I would want my name on.  I have rebuilt a few that were done by other shops and did not like what I saw.  There was a lot of welding on the cases that was needed so that the transfers would match up and for the relocation of the studs.  The welding warped the main bearing pockets, cranks seal pockets and the case halves mating surfaces.  I think that I could do a lot better job of welding but there will always be some distortion no matter who welds it or what type of welder is used.  Welded cases will never be as strong as the original cases.  

The 250 R crankshaft does not have enough mass in the crank webs to make the ports work optimally without having to do some really radical things to the ports.
 
I believe the 250 R crank web diameters are too small for the stroke that is necessary.  The distance from the crank pin hole to the outside of the crank gets too thin to be able to put the interference fit that is necessary for a crank not to flex and crack in that area.  Welding the pin does not stop the crank from flexing in this area it just keeps the pin from moving in the crank pin hole.   I have a few customers that have had their cranks stroked to 77 to 80 mm and have not had the crank pin hole crack or the welds break but these were not high HP engines with much time on the crank. With the limited amount of room in the cases and the large number of split crank pin holes i have seen, I do not plan to start building stroker cranks or stroking existing 250 R cranks that are destined to premature failure.

I would keep your 350 and get with a motor builder that can give you a good engine combination (ports, pipe, head, carb, etc) if you want to make some respectable power.  I would not trade what you have for the 400 pilot cylinder engine. If you trade your 350, I think that you are about to start working/paying on the same education that the current pilot 400 owner is tired of working on and paying tuition on.

[Shawn]

I don't now the history of the motor how do they run do they make a lot of horse power with the 89mm bore + I did not get the old crank so I don't now what the stroke is but from the top of the sleeve to the bottom of the exhaust port it is 77 mm any body have any ideas?

[Pumashine]

I'm using a +4mm hotrod crank with the yfz490 rod.

[Shawn]

how does it run

[Shawn]

u have a puma?

[Shawn]

do u think I should build this motor or is it a wast
 of time?

[DnB_Racing]

do u think I should build this motor or is it a wast
 of time?

I don't know about pilot cylinders
BUT
that would be your decision,

 if  what brings you pleasure is knowing you have something different then most and what it took  to get that then no,
 if your just looking for a big bore that moves the ground then yes.. but no one can tell you what YOU like and makes you happy

[Pumashine]

do u think I should build this motor or is it a wast
 of time?

I am skeptical of the 89mm bore you have. I got a pilot conversion bottom end on ebay for $700. I bought a pilot cylinder for $200. Got it built for trade work. Bought +4 crank and had it balanced for $500. Piston is $150. Got an ESR trx9 pipe and modified it at another $400. So I have at least $2000 into it. No one is ever gonna want to buy it. For $1000 you can get a new Puma cylinder and be much further ahead as it will sell for what you paid for it. No headaches or custom pipes. I say steer clear of any pilot conversions. I have heard anything built by FTZ was slow anyways. I love my pilot cylinder but have $1000 in port work done to it. So I would say it cost $3000 for a pilot conversion verses the same for a puma you don't have to modify other than the crank.

[Shawn]

OK are they a good drag motor ?

[Shawn]

were can I get a puma cylinder at?

[Pumashine]

were can I get a puma cylinder at?

Only problem you have is your bottom end cannot be used for a trx cylinder. Money wise you are a little further ahead by getting a crank and pipe. But if you were starting with a 250r bottom end it would be very easy to go with a puma. There is a member on here rsss396 who is a CP Industries dealer who can get you what you want.

[Shawn]

I will get a set of case thank u very much.

[ledperformance]

I will get a set of case thank u very much.

The Puma and Sphinx cylinders out perform cylinders such as the pilot cylinder. These cylinders have a much more efficient transfer port design and are in fact more state of the art than even most modern oem MX cylinders. The Sphinx  has 7 transfer port windows and the Puma has 8. The additional windows do a better job of controlling and focusing the steams of air and fuel being discharged from the transfer ports. This keeps the fuel/air streams from spreading out and getting disorganized as they move across the top of the piston and head towards the rear wall of the cylinder. They maintain  better  better column inertia, which is critical to prevent fuel loss out the exhaust port, especially a lower engine rpm's. These cylinders implement a triple exhaust port lay out which maintains a good balance of exhaust and intake port area. An example of efficiency is a Sphinx 350 with 186' of exhaust port timing will make more hp than a conventional cylinder with 190' of exhaust port timing. Of course you can imagine what would happen if the both had the same timing! The Sphinx / Puma cylinders have better low and mid range power even when you run higher port timings. If you for example ran 190' of exhaust port timing on both Pilot and a Puma, the Puma would make more Peak horse power and still have better low end and mid range power.
In short don't waste any resources on a pilot cylinder!