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My stroker project

2369 Views 2 Replies 2 Participants Last post by  HelicopterMike
Hey Guys,

My name is Mike and I am new to this Forum. As a matter of fact I am new to Forums all together, however I have been asked my a few people to talk about my latest project and I will do my best to keep up with my progress. I usually shy away from this stuff, but I noticed there is not a lot of info out yet on major engine mods and swaps. I have spent years building engines, working on cars, etc. The majority of my work has been on cars, boats, aircraft, heavy equipment, etc. I have done a few restorations, engine swaps in older and newer stuff, etc. That being said I have NOT done much on motorcycles, but many of the basic principles are the same on the mechanical side, however I am no expert. I am always open to others ideas and input.

I purchased my Z125 about two months ago. I had all of 100 miles on it before I ripped into it pretty deep. I love the bike, just want more power! I live about 6000 feet above sea level, (near Denver) so I am already loosing roughly 20 percent of what some of you guys have down on the coast. Even at that I want this thing to be much quicker than it is, not louder, not different looking, in fact maybe not even much faster on the top end (ok maybe a little) but the acceleration sucks, and pulling up any mountain hills in colorado is not fun when you have some guy in a motor home trying to pass you. Ok enough about that let me tell you what I have done...

Three days ago I removed the engine and installed the stroker kit from MNNTHBX. This setup had the larger piston, race head with much larger valves, higher lift and duration cam shaft, roller rockers, lightened primary, etc. It's just the same as the "big bore" kit, however the stroker crank (for those who don't already know) allows the piston to move further up and down. On this engine its not much, about 4mm if I remember correctly. In the car world this typically gives you much more torque, but it can be a trade off for top end RPM. In this case this engine still redlines at the same RPM as stock. I also installed the MNNTHBX air intake "Mtake" as they call it. The race head came with a larger intake manifold but I am still using the stock injector. I also installed the Yoshimura RS-2 exhaust and Bazzaz fuel controller along with the Bazzaz Z-AFM self mapping tool. Only pain with this was I forgot to order the larger 18mm bung for the exhaust and I didn't want to wait for one so I made one with some left over stainless I had. Last I installed the heavy duty clutch kit which I purchased online from steady garage.

I finished up the bike this morning and started it up. This is my first time using any fuel injection software, so I am learning as I go. Many hours on youtube have helped me on this. The bike started right up. The exhaust seemed louder to me than what I was expecting, but I fall into a small group that actually likes how quiet the stock setup was. I started up the self mapping program and rode the bike around for about 20-30 min total. It ran rough at first as expected, but started to smooth out at the end. I also had one of by friends ride it for another 10 min or so and he said it was smooth through all gears at that point. We plugged it back into the laptop and just saved the recommend changes. Unfortunately that's all I had time for today, however I have a long ride planned out for tomorrow. I currently don't have a dyno I know of around me to give you all hard data, but I will be looking for one soon. I do have a friend who still has a stock bike, so we can run them both in the same environment and see the difference. Hopefully this will help some of you decide if this is something you want to do or not. I would like to find out just what the bike did with all the mods minus the stroker crankshaft. Changing out the crankshaft is significantly more work than just a top end big bore kit, so I feel this data would play a large part in helping someone decide if its worth it or not. I welcome any questions anyone has because I will be asking plenty myself as time goes on. Look forward to hearing from you all!
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Can't wait to hear your thoughts, and thanks for the post. Once tuned,
I think you'll find it's a screamer. Let us know if you need any help along the way. Enjoy.
After riding for a few hours today it's definitely a screamer. It had no problem doing 65mph up some very steep hills where the stock setup would not even do 35-40. The limitation is gearing at this point. I plan to keep this setup for another month or so then I will be selling it to start on a 300 swap.
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