FATAL1TY - X

How it all began - It was in my mind for 2 years. Didnt got the spare time and budget to do it until now. I home ported the spare block i had months ago for this. For starters its called a bigbore mod. But for the enthusiast who want the long answer, its called shogun piston modding a RX100 block. the shogun piston is ligter but larger(52.50mm vs the stock 50.00mm). but the block needs to be heavily modified to accommodate the (about)10 mm shorter shogun piston. Compression height is vastly off. All the work except for reboring and cylinder block milling is done by me.

I'm new to the tuning front. But i always felt tuning is more than just a performance air filter and an iridium spark plug. so sourced a bored out block from a friend for free, that is 3 years ago. everything was preplanned except for some vital data.
1) I had no idea about the specs of a stock shogun piston(asked for help here, and as usual, no one replied!).
2) I don't know the difference in specification b/w the Shogun engine and RX100 engine.
3) I had no previous experience. (also called a noob)

so, putting my engine at stake, i decided to work on it one day. Stripped the whole engine in about 1/2 hours and started to examine the parts for wear. I wasnt a slow rider. i never properly runs in an engine even though i know the risks. so was expecting some mild seizure marks on the piston.

All parts removed and ready to examine.


Small end had a little play. so concluded that piston pin and/or bearing is shot. Big end was fine as i did my recent bottom end rebuild a year or so ago.
Now, the surprise was that the piston didnt showed any abnormalities. It was of the brand Goetze. This brand of piston is not a favorite among enthusiasts. but it handled the power from a polished and piped block. Looks like Indian brands are getting better!


Exhaust side. Some normal scoring marks.


Intake side. it was also looking good.


Piston dome. Its a first oversize piston.


Later that day, i went out to look for the shogun piston. after searching for a while, i found a 52.75mm(1st oversize) SAM piston. Now before you all bash me for not going for an ART piston, let me remind you that in Kerala(not just Kerala, almost in every part of india), not much people are aware of performance parts or tuning. so availability sucks. And also, i didn't knew how the build will turn out to be. so didn't wanted to spent a lot on performance parts and later blow it all up. Piston kit included piston, rings, piston pin and circlips.

I went home, and it was measuring time. the first thing you'll notice is how light the shogun piston is comparing the 100's. placing them both on a level surface brought out new challenges for me. Shogun piston deck height is about 6-7mm shorter than the 100. 100's stock piston came with ported skirts to increase intake duration but shogun piston is not ported. The "feel good" part was when i found out that the skirt of both the pistons where about the same in length(Shogun piston had just about an mm shorter skirt than the RX), Shogun and RX piston has a same diameter piston pin and that shogun piston has a taller dome.


After getting those crucial numbers i needed for this build to happen, i decided to mill 7mm from the base of the block and an mm from the top of the block. That will even out the piston deck height to cylinder height when at TDC, gives me better compression and also increased intake duration. Went to the lathe shop, and after lecturing the lathe guy in every possible way i could on how important "Precision" is crucial in this job, he said okay. He told me to drop by 2 days later. And so I went home.

Later that day i decided to map the stock cylinder block. after a lot of time and paper sheets away i got it just about right. Now, you cant do much with a divider and a scale. can we?


The next problem i came across was with the small end bearing. Shogun piston had wider pin supports than that of the 100's. So when using the stock bearing along with the shogun piston caused excessive play b/w the pin supports and bearing, which can result in bearing failure as now bearing is running around instead of staying in a place! Refer the below pic.


So again, i was puzzled with questions. After a while, i decided to go for Shogun's small end bearing. It also posed a slight problem. As the shogun piston small end bearing is longer, it will protrude out of the small end of the RX conrod 2-3 mm. Decided that it is much better than a bearing which runs around in its place. The Shogun bearing on the left in the below pic is a new bearing . it cost only 50Rs. And out of the box it was rusted and after a while handling it for measuring a roller came off. I guess i'm contradicting myself, but some Indians quality still suck!


So, decided to look for an original TVS small end bearing. after searching for a while i found one. Now, that was quality. the roller supports where made so that it will lock the rollers in their place. It was also machined much better and it also cost 100+rs.


The next difference is b/w the piston rings. Shogun uses thinner rings in comparison to the RX100 rings. in the below pic it is not very evident, but in person it is.


After 2 days, i went to the lathe shop to get my "Gunned" block back. at first inspection i thought he did a great job. machining looked fine, he chamfered the sleeve. everything looked fine except for 2 new ports opening up on the intake side of the block and a slight difference in thickness b/w the left and right side mating surface of the block. i told him to clean the mating surface up. he did that in a jiffy and i left home with my block. Now, what the hell am i going to do with the "New" ports? that was in my mind.


After placing the block on the bottom end i decided that the "New" intake ports wont be a problem after fixing the cylinder. the problem was with the four fastening holes. After all that machining it had became too thin. Too much tightening torque and i will end up breaking it.

Here is the original block on the left and "Gunned" block on the right.

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2002 Herculese Top Gear 6 speed
1990 Yamaha RX110
2010 Yamaha YZF-R15

2007 Suzuki Alto Lxi

Noor

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FATAL1TY - X

Still had to source some more parts before i starts assembling the block and piston. Also there is the issue of high rpm gas flow as Shogun piston didnt had ported skirts. I was not planning to physically alter the piston in anyways as these cheap pistons are not guaranteed to stay together once it is physically altered. so decided to do some porting to enhance the midrange and bottom end performance. I wont describe exactly what i did. but the Boost port, the Transfer port and the exhaust has undergone changes. Also i has an EC tuned for midrange lying around to sweeten the whole deal. All this with increased compression should make things interesting. So bought 2 filing rods, one with a square profile and one rounded and started the work. I already did some porting a few years ago improving them(ports) as i learned new stuff. Now this will be the final addition.

Block before and after altering. you can see what i did with the transfer port bridges. It was a 2 hour work using hand files.


After the final checkups like the clearance b/w the head and the dome and port timings it was time to get things running. After the rest of the parts was sourced, the assembling began. It was my first time engine assembling. used a lot of anabond and carefully started assembling the parts one by one.

The piston kit.


Gasket placed.


Time for the piston to be assembled. Oiled everything up and assembled the Rings properly. Took some time to get the circlip in place. it was a stubborn little bugger.


Now the block is about to go in.


Again used a lot of oil and fixed the block. Used Three ~2mm washers on each crankcase bolts to compensate for the lost metal from the block. also assembled the head.



Now all that was left was The carb and exhaust. Carb has been upjetted and the airbox has been modified to increase airflow and fueling. Also running an YEIS.

I fixed the stock exhaust, just to see how the engine works without the added stress from fixing the chamber.


Finally the tank went in. filled a liter of fuel with 35ml oil.


Now it was time for the first start. My first Top end engine rebuild + Tuning attempt. I was having a thousand butterflies flying around in my stomach. was so tensed up.


My friend was there to see it happen. I kicked the kicker and nothing happened. Few more kicks and still nothing. my face was getting pale. adjusted the idle screw, pulled the choke, double checked everything. Again started kicking. i thought it needed some more kicks to get the crankcase pressurized. After about 5-6 kicks after pulling the choke it came to life! now adjusted the idle and now it settled to a "steady" idle with that trademark 2 stroke pitter patter. Imagined the engine internals in mind and reviewed everything again to make sure nothing went wrong. Everything is sound as far as i know. Turned the key off, and kicked again. then it started at first kick itself and it still does! first thing i noticed was the increased compression as now it takes more effort to kick. Took it for a ride and the torque was evident. pulled clean till midrange and it was a very good feeling. My cousin with his stock RX came around. i told him to ride it for a while without going monkey on the throttle. he rode it, got back and asked. "What the hell did you do?! it is faster in every gear!", i told him that is because of the RX135 4 Speed sprockets which my 100 uses. he was now confused as my 100 is geared taller and still pulls better than his stock 100. The look on his face was enough for me to be satisfied.

A few days later, i switched to EC. the sound was just ear popping, the increased compression has made things louder. it also has a shorter stinger and so cant use much glass wool to muffle the sound. But i like it this way! Now with the chamber, i'm getting better output from the setup also better fuel efficiency! which is a not so common phenomenon among ECs. Fuel efficiency figures when under normal conditions is 35+ and go WOT it still delivers close to 30kmpl.



Finaly i would like to say that it was all my own effort. Asked for help and i didn't get any. All that i knew was that it can be done as i saw some posts where they mentioned they did it with good results. So it was all a one man show from the beginning till the end. Did the homework my self, broke some parts and learned everything the hard way and all that effort finally paid off.

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2002 Herculese Top Gear 6 speed
1990 Yamaha RX110
2010 Yamaha YZF-R15

2007 Suzuki Alto Lxi

insane_x97

nice project bro, All the best...
and give a second thought to piston intake holes, sam is cheap but not that bad..

FATAL1TY - X

Project has already been completed, a month ago. i just posted it now. everything is fine. yes, the intake holes are a problem. but the setup works efficiently at the midrange and that is where it produces most power. now with taller gearing(rx135 4s) it is faster than a stock 100. fuel efficeincy is superb. about 40kmpl if ride normally and returns above 30 even after some serious ripping. i'm loving it more than my R15 now! R15 havent seen much road for weeks now because of RX110

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2002 Herculese Top Gear 6 speed
1990 Yamaha RX110
2010 Yamaha YZF-R15

2007 Suzuki Alto Lxi

abhishekch

nice performance mode on rx100.. o sorry now rx110 .why not 5speed gearbox of rx135..

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insane_x97

might be fun to ride,a wolf in a sheep's clothing....

FATAL1TY - X

budget constrains.

__________________
2002 Herculese Top Gear 6 speed
1990 Yamaha RX110
2010 Yamaha YZF-R15

2007 Suzuki Alto Lxi

insane_x97

how about three sprockets and changer drum, but fun continues...

FATAL1TY - X

where can i get one? the idea of this is so that we can change the sprockets without much hassle to run different configurations. right?

__________________
2002 Herculese Top Gear 6 speed
1990 Yamaha RX110
2010 Yamaha YZF-R15

2007 Suzuki Alto Lxi