Thank You! You can call me Nitin, I am still on my milk teeth

You mean for the re-build or for front sprocket change? For re-build, I sat with him only on the day bike was being assembled. That is, after all the parts arrived from painting.

For replacement of sprocket, I just left the bike in the evening and picked it up the following day.

After 26 years and 1.6 lakh kms, I had to give it a full engine re-build. I had no option actually, the crankshaft bearing seized. I have no idea why it happened. Oil supply was correct and the pump was/is working fine. Some of my friends told me its just the age of the machine, maybe. Ideally, it needed a top-end job three years back itself when I started this thread. Back then even thinking of running on re-bored cylinder was scandalous! and I was not too keen on using up my new bore.

Thanks to Vijaydeep I took the huge leap of faith this time.

Following works were carried out:-

1. Re-boring the cylinder to 1st oversize.
2. Re-placing crankshaft along with full bottom end re-build.
3. Complete clutch re-build.
4. Chroming silencer

Cylinder was measured using a bore guage and the measurement read 50.06mm. Like I said three years back, there was some noise coming from the bore too. After looking at the old piston, I think the rings had failed and it looked like there was a partial blowby.

Crankshaft was bought brand new in 2009 exactly for this purpose :-) But I didn't know I would have to use it so soon.

There was no problem with the clutch really. Just a bit of play in the bell but it would have been harmless mostly. But then, I thought of getting that too for the sake of completeness.

Chrome near the tip of the exhaust had peeled off thanks to Pacer Yamaha's washing! It looked odd so I got it re-chromed again at Paramount.

Now picture time.

Mahle piston. I forgot to take picture of the actual piston I have the same make pistons in .5, .75 & 1mm. If anybody is interested I can take snap of one of them and post.


OE Crankshaft




Engine bearing set


Engine oil seal kit


Imported clutch bell & primary. Expensive and can be avoided if you can lay your hands on regular Indian OE stuff.




Fibre friction plates


I got the idle screw zinc plated (my technician tells me it is zinc plated with silver finish) because it had started to rust. The newer idle screw have ugly big head which I dont like.





Chromed silencer



IND Plates. I know the purists will argue otherwise :-)



Parting shot


Small video on the day I took delivery.

RX-100 Post engine re-build. Rev at idle - YouTube


As of today the bike has completed ~430kms of running in. The best way to describe its performance would be 'sweet'. Well what else can you say when you can't go past 1/4 throttle :-D. It is smooth, no unusual sound and things are fine so far.

I am running on Shell petrol with 2% premix and Motul 510 in 2T oil tank. I didn't bother hunting for Motul Motomix or any other mineral oil for the sake of running in period. Was just too lazy.

The whole thing was done on a turn key basis by my technician. I only gave him the parts. This time I didn't run around for parts also. That was taken care by a well meaning fellow stroker :-) So my only involvement in the whole project was calling my technician to know the progress and putting up a post here :-D

Awesome RX 100 bro really fantastic the paint job is flawless ..... DTW has showed their magic touch as usual

Thats not the OE idle screw on the RX-100, its more of the 135. The RX-100 came with a simple flat spring loaded screw.
Am also not to much of a purist and like a few things to be updated with times, in this case are the no.plates and there is no harm in going for the latest ones. I have a soft corner for the RX-100 and especially when its red. You have a beautiful bike there, preserve it like the way its meant to be.

@Dinesh.P: Please refrain from quoting along with all the pics

@Nitin - A W E S O M E !!!!!!
Painting, chrome plating finish is way too good! Can you check the stock piston if that is a Japanese one? Cause not many here are fortunate to have a 80's RX100 and running in stock bore. The Red color still lingers even after closing my eyes. Good job. Next time when I happen to visit Bangalore, will not miss to see it in flesh.



Asif - Probably you were not aware. If you look at the bikes of 1986-93 the carburetor were Mikuni Japan. The idle screw will be star/flowery type. Later, Mikarb started to supply for post 1993 models which had the minus type idle screw. What you see in Nitin's idle screw is 1000% authentic Japanese idle screw of yester year.



I would have told the same. Everybody who reads the post would be aware of the context or you could be be specific while quoting member's post.

@Sriram: I don't think so.
Mine is a 87 model and I have that flat head screw on the bike from when I can remember. I had actually in my school days tried to be over enthusiastic and tightened every screw on the bike once including the idle screw, later learning that it was supposed to be that way. Maybe am wrong but thats how it always been on my bike, which was a 100% Japanese make.

@Dinesh

DTWs paint work is very inconsistent. He has screwed up the silver bits because it didn't age well. However on my 135 the same silver bits are in excellent shape even after one year.
Unlike, cars sadly bike paint industry is not that well organized

Thank You Sriram. Sure, we will meet next time when you are here. Hopefully, you have a more relaxed itenary when you do come here next time

There is a hand of my detailer too in the appearance the paint Frankly, the silver bits (fork legs, crankcases, brake hubs, chain guards) haven't aged well.

Just to clarify, bike is NOT running on Y series bore. It is running on G series bore and had done ~68k on standard size. I'll post the piston pics in sometime.

Asif- Maybe 87 onwards the screw head changed or maybe yours was replaced. But this is the screw that came on the bike. Infact, 10 years back when he handed over the bike to me for college commutes he told me to be careful as to where i park the bike because some things like the idle screw (pointing to it) are not available now.

135 has a flat head screw. A pic from my 135:-

I have not seen any mikuni carb (Japan) having flat screw type idle screw. May be your carb is authentic and Japanese make but I doubt if the idle screw was changed in mean time.

May be I missed to read somewhere that it is not Y series. I was under the assumption that the bike is of Y series since it is 1986 make.

That's what I thought too. I've seen several carbs but the older ones always had the star type idle screw.

My 1998 model RX135 came with Mikuni (Japan) and has star head type idle screw and not flat head. May be the later models might have come again not sure from when.

Yup, bore was changed in 2002 itself. Unfortunately my father was conned out of it :-(
My 135 is 2002. Going by this, I think Yamaha has introduced and stopped this screw several times.

All localized carburetor had simple flat head screw. ie: like micarb and ucal carbs.

Mikuni carbs always had star type flower head idel screw .

Sriram yes I am having a 1992 RX 100 having Mikuni (Japan) it has a star head type idle screw and also my 2000 model RX 135 has a star head idle screw.......


@All: Sorry for quoting all the images.....

Finally, completed 1000kms running in. Did not encounter any problems and the bike was sweet throughout. I gave for servicing two days back, basically to re-tune AFR and 2T oil flow post running in. I checked mileage only once during running in and it was ~34kmpl.

The only niggle in the bike is the irritating noise coming from the fuel tank cap. It is reduced greatly now but still audible. Not breaking my head too much over it though.

With this I retire the bike from its one month commuter duty. It will be used only on Fridays and rest of the weekdays my 135 will do the commuting duties.

Planning to do a short ride to Bhoganandeeshwara temple on one of these weekends. Will get to know how it runs at high speeds. Besides I need to give it some space to stretch

Re: COSMETIC REBUILD: Yamaha RX100 1986 (now engine rebuilt)

Well, a lot happened from the time I retired this bike from its daily duties. Restored a RX135 4Speeder, bought a Duke 390, married, became a father...in all this the bike was neglected for close to three years.

Now, due to the change in my work location (Bellandur ORR via KR Puram where 390 becomes a liablity), will be bringing it back to commuter duties.

This is how it looks now:-





1st Over-size Mahle piston, brand new crankshaft and new clutch. Thats the engine set-up I left it off at three years back. Had just finished running-in.

Rode to work past week and the performance is sweet. Fuel lid lock noise is still there except that it doesn't annoy me as much. Cosmetically, it is not perfect. Outer sides of the rims has picked up surface rust, clutch cover, magneto cover, brake drums, etc the silver paint has chipped of here and there. But not going to get anything done for now.

Renewed FC also past week. Good to go for another five years.

Re: COSMETIC REBUILD: Yamaha RX100 1986 (now engine rebuilt)

Good to see her back. And good to see you as well.

Re: COSMETIC REBUILD: Yamaha RX100 1986 (now engine rebuilt)

I went on a short breakfast ride this morning to 'Pavithra Idly Hotel' Tumkur. It was around 150 kms round trip.

Left home around 6:15 AM and took the usual Mekhri Circle-Yeshwantpur-NH4 route. Took a bio break and clicked few pics. Apologies for the bad pics.









Bike performed well. Average cruising speed was 80kmph. Top speed as per the GPS App on my phone was 90kmph. I never tried for top speed run, didn't do WOT and ducking,etc. Rode well within the bike's limitation.

Previous tankful of 10 litres got me as far as 368 kms.

Lot of muck in the fuel tank. Looks like rust particles. Infact, the previous evening I got the carb cleaned as the bike was behaving as if it was in reserve.

Need to get the tank cleaned thoroughly. Possible replace with new one.