Invincible

Hi guys

I had the biggest crash of my life almost at the same time when xbhp’s server had; so could not hang around xbhp like before (=>I am single no more )

To the point, I ride an A150 -2007, 29k on odo. I had spent a lot on my bike. The following are the changes I did to my bike

Looks : Replaced rvm, turnlights and grab handle with that of RTR’s, changed seat to step up type, had some RTR stripes on it, scrapped the chain cover and replaced with P200’s plastic one.

Performance: K&N air filter, Automech Exhaust, Porting, polishing and valve cutting, Boring up by 1 mm (+5.2 cc) using SamKrg piston

Others: Hella car horn - replaced srichakra with MRF - Running on Motul 300v



Filter was changed right at 2000 km and exhaust was replaced at around 21000 km on odo. There was hardly any change in acceleration after filter was fitted. Initially, it was sitting on the airbox. Then I tried to mount it directly on the carb, when I did so, there was a noticeable difference in acceleration but the top end got a big blow (would not go beyond 95kmph). So I repositioned it back on the air filter box. The top end slightly increased, as the filter could deliver more air at high revs, when the engine is desperate for it.




Then after a long wait for the bent tubes, I got the exhausts fixed by automech engineers. There was a significant improvement in the top end power and I could touch 120 with minimum effort. The mid range is awesome and I love the way it reaches 95 from 65kmph. And needless to mention, the exhaust note is just awesome. Also since the gases are ‘free flowing’ the vibrations dropped significantly and along with motul, the engine was breathing so smoothly with almost nil vibrations.





Then began a long journey in search of a good mechanic for the engine job. Search for some tips on xbhp only made me jealous about the Bangalore xbhpians’ easy access to bike modifiers. Not many experts seem to be put up in Mumbai.

I finally found one mechanic doing the cylinder job (just 2 km from my office!). But just like any other mechanic, this man though experienced hardly knows about the technical aspects of the job he slogs on all day long. But still I inclined on his experience and opened up my engine for him. The deal was porting, polishing and valve seat cutting.

I also enquired about the reboring. As obvious it is, getting an upsize piston was the challenge. He told me clearly that he cannot bore the cylinder by more than a couple of mm. I wondered how some others managed to shave above 50 cc from the cylinder? I guess anything more than that limit would need a new engine block.

After enquiring and searching Grant Road, got my hands on the Suzuki Fiero’s piston (bigger by 1mm – last size) manufactured by SAMKRG and it was now the mechanic’s job to scrap an mm of metal round the circumference of the cylinder.

The last two days I had my fingers crossed as I knew any small error would ruin my engine. I know I might come up with a host of other problems with the engine but I know its fun to take risk in life. Meanwhile I had tried to find a suitable jet to ensure better flow of petrol but as guessed, hardly any auto shop owner understood what I asked for. All I new is Apache’s jet size is 102.5 and I confirmed later with a TVS spare parts outlet that RTR’s is 105. There was no stock of 105.


Back from the shed, now I am done with the porting and boring job. There is certainly a good improvement in the bottom end, but the mid range does not have to be improved much. I have not dragged her above 60kmph so I could not really assess the performance difference. Will keep it posted here. All I expect is a 1 bhp more out of all these mods and anything more is a bonus for me.

My question now is the popping sound in exhaust (which started right after I changed the exhaust) seem to have increased heavily. When I decelerate, this becomes too loudly. Though it sounds cool I am sure something is wrong with the carb. In some websites, people say it is because of lean mixture (fuel suddenly shut off – partial combustion of the escaped air) others say it is the rich mixture (fuel escaping into the exhaust and burns there).

Can someone tell me how to get rid of this, if it can help in improving the engine performance / life? Also can someone tell me which main jet of around 115 size would fit on the bs-26 carb? Or RTR’s 105 size is fairly enough?

One more quick question: Does worn out clutch plates affect speed? The mechanic says it will lead to drop in performance.. I am asking because I dont 'feel' anything wrong with my clutch plates..

Last help I am expecting is if someone could throw light on how the valve timing change/ advancing is done how to get maximum out of the previous mods by changing the cam.

Aryan

Query Moved and Approved.

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M.R.B

Thats a lot of work done .... whats the Compression you are running now?

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M.R.B
Bajaj 150 - '71 | Yamaha RX135 '98 | Apache FG '06

HydBiker

lots of work and still unfinished... I'm sure u'd get good guidance here to finish the nice job u have started

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Invincible

I know it matters a lot, but how to measure/ calculate it?

johnjojo08

good work man..

chicane1879

Welcome back to xBhp, santosh!!

Yeah worn out clutch plates affect performance a bit, as your bike has already covered close to 30k it would be better if you replace it. The bike will run much better and you would only note the difference after you install a new one!!

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Invincible

Thanks Chic! I would replace them during my next service.. Before that I have to place an order for the RTR's main jet (which they usually dont have).

velociraptor13

hi santhosh,glad to see u alive and kicking and thats a whole lot of mods u have done.So finally u were able to get the automech.Btw how about trying out the unicorns mainjet (115 number).I have one lying with me in spare,as i am currently running on tbirds jet.But i doubt it wud be a overkill.

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Joel

if you have only put a 1mm piston, then the compression will be almost the same. hardly any increase.
The Fiero/Apache ports need to be properly worked on. Enlarging it beyond requirement will ruin the mid-range.
Also merely enlaring the port/polishing is not the right way.
What dia primary pipe are you using for the exhaust?
Also the valve cutting etc that u mentioned is just part of normal head overhauling. Nothin to really bump performance,.
On such sidedraft heads like on the Fiero/Apache(its the same head), polishing will further ruin the gas flow.

@MRB - The compression ratio on this set-up will now be, still under 10:1. Thats hardly gonna be noticable.
The bike will sure give a lot of psychological gains in terms of performace and indeed the freeflow exhaust and filter would gave given 1bhp for sure.

Edit - About the jetting part, 115 mainjet will choke the hell out of that carb.
Just set the needle to the richest position. You dont need the 105 jet. put it in the 3rd slot.

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