putting a wiseco 10.25 to 1 piston in my 85 350x

[kylem1184]

My motor is stock. Looking for a boost from my research. Going to a 10.25 to 1 will give me what I am looking for. I want to stay with the standard bore. So I'm curious what else will I have to do to my trike if I put this piston in it will I have to change anything else. I have also been looking at going with a 400ex carb. Any help would be greatly appreciated.

[barnett468]

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You need to have the cylinder bore professionally measured . . if it is out of round enough and/or has enough taper, your new rings will not seal . . if it is within spec it will need to be deglazed properly with a ball/bottle brush type hone.

If your bike is currently properly jetted, I would go up one size on the main jet then check the plug color after around 20 minutes of riding . . extremely light tan to medium tan is good . . almost white, very dark tan or black, is not good.

Try it with and without the air box lid to see if the power changes . . it may sound louder and more powerful without the lid but that doesn't mean anything.

Increasing compression alone will not give you a significant increase in power and in fact, you may barely notice it but it definitely will give you some.
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[barnett468]

If you still have the orig air filter I would buy a uni filter orig style replacement . . you can get them online direct from uni filter

[barnett468]

If you have the stock muffler and you do not need a spark arrestor or need it quiet and you want more peak rpm, I would get a non arrestor type silencer.

[kylem1184]

I have a DG pipe and have a newer uni air filter. I'm not looking to spend over 500. What would you recommend. I'm 6 foot 3 and 290 pounds the trike pulls me around ok but as we all know I want more. What would you recommend?

[John Tice]

I’m not much of a 4 stroke guy; is your cylinder plated? You need to be very careful when fitting a Wiesco piston. If you buy a new one, very carefully check the skirt clearance making sure that the fit is correct before you muck things up & are unable to return it. Same goes with the rings; the incorrect rings have been packed many times. I’ve been using the FINE Wiesco products for many years but you must keep a close eye on correct packaging.
This is my first post in 3 wheeler
JT www.smallenginemachineworks.com Take a look

[barnett468]

I have a DG pipe and have a newer uni air filter. I'm not looking to spend over 500. What would you recommend. I'm 6 foot 3 and 290 pounds the trike pulls me around ok but as we all know I want more. What would you recommend?

ok. well this is a different deal altogether and there are a few different options and others will have ideas also.

1. the bigger the engine, the ,ore power ot will have if everything else remains the same . . which means that if you install a stroker kit, you will have noticeably more power, however, that is a very expensive deal.

2. in general, installing a numerically higher gear ratio will increase the acceleration rate of a vehicle but it will also reduce the top speed a little and also cause it to be shifted slighter sooner in each gear.

3. in general, installing a "bigger" cam simply raises the entire operating range of an engine . . for example, if it had decent power from idle to 4000 rpm with the stock cam, it might have decent power from 2000 rpm to 5000 rpm with a moderately bigger cam, so you loose some power on the bottom but gain more rpm and power on the top end.

4. one option for you is to install a 1 tooth small front sprocket and see how you like it . . i definitely think more compression is also good but keep in mind that you will need 91 - 93 octane with that.

5. if your muffler/silencer has a spark arrestor, you will have more top end power without a spark arrestor.

after you do these changes, you can decide if that's enough power . . if its not, then installing a slightly bigger carb is a good idea . . if thats still not enough then a bigger cam is the next practical option.

if you get to this point, you may benefit from having the cylinder head ported a little.

if you still want more power after that i think a small bottle of nitrous should get you there.
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d an othis means that

[RIDE-RED 250r]

Mr. Barnett has some good advice and I concur.

Having said that, my wife's 350x is stock other than a K&N and DG full exhaust. My brother has a 350x as well, same exhaust and air filter but has the exact piston you are looking at.

You can really feel a difference between these 2 trikes. Top end is practically identical as far as we can tell without running them through a radar trap. But the acceleration on brother's is noticeably more powerful, hands down. The only drawback that we have been trying to work through for quite a few years now is that his X seems to have a slightly lean condition just off idle. Imagine just putting through the woods in 1st gear with just enough throttle to keep the engine from laboring too much to stay running as you are underway. That spot and that spot alone it seems like it is almost trying to run against itself. We have tried jetting, synchronizing the carb and everything else you would typically check. It doesn't seem as though the bump in compression would cause this with no cure.. Anyhow, I digress... Other than that one small throttle position, it runs amazingly strong. I would be curious if anyone else that is running the 10.25 piston has experienced the same thing.

We haven't done the 400ex carb upgrade on these trikes yet, but I have a friend who did. He is a member here but doesn't post much. He is very happy with the 400ex carb. Ended up settling in on stock 400ex jetting specs. Carb does require a bit of persistance and shoe-horning to get in there. I do not recall if he has upgraded exhaust or not.

I plan to do the 400ex carb on the wifes ride fairly soon...When I do, I willpost a thread with pics as there doesn't seem to be any on here last time I searched it.

[BOB MARLIN]

I run 10.25 to 1's in all my 350x's. There is a noticeable difference in the way they run. I don't know if there is really any increase in HP, but they just run better over all. Responsive and crisp is how I would describe it. By the way, you would be far better off buying the oversize piston kit and spending the $60 or $80 to get the cylinder bored rather then put a brand new piston in a 30 year old bore. It's just not going to work well.

[barnett468]

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The short explanation is that increasing compression will increase the "power" throughout the entire rpm range, but as mentioned. it won't be drastic . . I have done back to back seat of the pants comparisons way more times than I can remember . . If an engine has less compression than it did originally for whatever reason [which is obviously commonly due to worn rings and cylinder bore] and one bores it out and installs a high compression piston, it will make a much bigger difference than simply installing the same size high compression piston into the same size bore on an engine that has not lost any compression because you will have made a much greater increase in compression on the worn engine so in this particular instance, it might seem that the high compression piston made a big difference but some of the increase in power also came from increasing the engine size and compression with the bigger bore as mentioned below.

Just boring out the cylinder will increase both the compression AND the engine size if the volume of the dome on the new piston remains the same which of course will both increase power.

Also, the more compression an engine has, the more "volumetric efficiency" it has which is basically the amount of intake charge it takes in per cc or ci . . The larger the intake charge, the more power it will make because there is more fuel there to make the combustion/explosion with . . Also, the more the intake charge is compressed, the more power it will generate . . For a poor example, if you take an ounce of gunpowder and put it in a sealed 10 gallon can with a fuse and light it, it will just make a light poof sound that you won't even hear [or so I've been told, lol]

100% volumetric efficiency means that an engine takes in an intake charge that has the same amount of volume as the "swept" volume of the engine . . It's a bit had to understand and even harder to explain but there is no production engine that is 100% volumetrically efficient, however, it is possible to not only increase the volumetric efficiency of an engine with more compression and exhaust that has more scavenging etc, it is possible to build one so it is MORE than 100% volumetrically efficient.

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[barnett468]

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POST CORRECTION/ADDITION BECAUSE I STILL HAVE NO EDIT BUTTON

For a poor example, if you take an ounce of gunpowder and put it in a sealed 10 gallon can with a fuse and light it, it will just make a soft poof or sizzle sound that you won't even hear . . If you place it in a one pint container, it will make a little noise and pop the lid off or expand the container a little . . If you put it in a one ounce container like a CO2 cartridge and then lite it, it would be best to run away from it as fast as you can [or so I've heard].
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