My 350x engine mod thread.

[jsimonh]

Alright guys, I've been gathering info and parts for about 2 weeks now and I'm ready to start my project. The goal was to pep up my 350 with some goodies. First up is a lightend flywheel from Ronnie (who is the MAN!).


Next we have the Powroll cam (mild/mid).

And finally we have the NEW stock piston/jug. And new valves with high performance springs. This setup is already under a change because after much personal debate I decided to go ahead and get a new 10.25 to 1 piston. It hasn't arrived yet so I don't have a pic.

I tore it down tonight and low and behold what do I find? A high comp piston already in there! SOAB! So now my old jug/w high comp piston will be for sale (pm with offers if your interested). I thought about reselling the new stuff but I already bought it so why not use it!

Alright here are some of the progress pics.





The only thing that has me waiting is the new high comp piston. As soon as it comes I will have pics of this thing going back together and then Hello Little Sahara!

So what do you guys think?

[ATCR250R]

Thats going to be one mean 350 you got there!

[random-strike]

pretty cool

[3wheelencowboy]

that's what i plan on doing to mine kind of i might go a little crazier though why not a stroker crank to??

[jsimonh]

Thanks guys, My major debate on the piston was reliability. I think this is about as far as I want to go. If a stroker motor wasn't always talked about as a "tme bomb" I might look into it. Maybe in the distance future?

The main thing that concerns me is that my motor wasn't hard to kick over . Then when I seen the high comp in there I was really thinking WTF? It ran great and had lots of power, but you could almost kick it over sitting down. The valves are pretty built up with carbon, maybe that had something to do with it? IDK, but it will all get fixed soon.
Is there anyway to tell if the cam is stock? The Powroll definatly has different lobes and they look bigger, but I'm not sure. I didn't see any markings on the cam, but I wasn't really looking to hard either.

[3wheelencowboy]

wow mine has the piston that you are going to put in yours and i literally have to put all of my wait on it just to get it to kickover definately sounds like a mean bike though what kind of carb are you gonna run??

[jsimonh]

Stock for now. I'm looking at getting a 400ex carb, but everything I read seems to make it sound like a major pain in the butt. If I can get one off of ebay cheap enough I'll at least try it.

[random-strike]

id get the 400ex carb, just need to jet it correctly to your application.

350x carbs are complete garbage

[3WW Star-Yamahondaman]

L@@KING GOOD !!!!
when you get your NEW Piston... try to round off the sharp corners where the valve pockets are.... i normally use a dremmel with small Cratex wheels ...
Keep the Pics coming !!!

[Mosh]

Stock for now. I'm looking at getting a 400ex carb, but everything I read seems to make it sound like a major pain in the butt. If I can get one off of ebay cheap enough I'll at least try it.

Make sure you adjust the choke detent.Re-tweak it to make it stronger.The 400ex carbs were bad for sucking the choke closed at high rpms,once they got worn out.It is a simple 5 minute fix.

[SWIGIN]

as for it kicking easy, do you have the compression release hooked up?

my 350x motor has a 12 to 1 that i milled to about 11 to 1 and with the comp release it kicks real easy.

with out the release it will kick like a mule!

[random-strike]

as for it kicking easy, do you have the compression release hooked up?

my 350x motor has a 12 to 1 that i milled to about 11 to 1 and with the comp release it kicks real easy.

with out the release it will kick like a mule!

you lowered the compression by milling the head?

[jsimonh]

as for it kicking easy, do you have the compression release hooked up?

my 350x motor has a 12 to 1 that i milled to about 11 to 1 and with the comp release it kicks real easy.

with out the release it will kick like a mule!

I have a decompression cabel, but it's never been on the trike. The part up on the head where it hooks to can be pulled all the way out easily. I'm not sure whats going on with it. That is kinda why I went overbored with all the new topend parts . If you replace everything then nothing can be broken .

[SWIGIN]

you lowered the compression by milling the head?

um....no......i milled the piston

[jsimonh]

L@@KING GOOD !!!!
when you get your NEW Piston... try to round off the sharp corners where the valve pockets are.... i normally use a dremmel with small Cratex wheels ...
Keep the Pics coming !!!

How far down do I smooth them? Just take the edge off a little? C'mon man you gotta hit me up with more details!

Make sure you adjust the choke detent.Re-tweak it to make it stronger.The 400ex carbs were bad for sucking the choke closed at high rpms,once they got worn out.It is a simple 5 minute fix.

Thanks for the heads up. I can't decide if I want to do the 400ex carb mod yet .

What does lightening a fly wheel do and how much does it cost? Whats the steps to do this? What are the pros and cons? Advantages, dis-advantages? The book says that if your decompression arm is not adjusted right, you could damage your valves. If that arm came out like that, it needs a new pindowl. Couple of bucks from www.partsfish.com.

I'm not sure just yet on what it does. From what I've read along with talking to NOS_350x(very cool guy) on the phone it is instant power . It will allow the 350 to rev alot faster, which makes it get up to speed faster . 10-4 on the pindowl I knew something was up with it just wasn't sure what. Get in touch with Ronnie (Yamahondaman) in this thread about the wheel.

No updated pics yet(still waiting on the piston). But I did buy me a digital caliper today and took some measurements of my new cam. Where or how do you measure the lobes? Powroll says Lift .355” Intake, .360” Exhaust I get the .355 by measuring the tallest point on one lobe but when I measure the other I get .430. I measured the original cam and cam up with the .430 also. The other lobe on the stock cam was shorter than the Powroll but those other two seem to be the same height. What gives?