SFM125 Roadster 2013 K157FMI Big Bore 150cc L230 Camshaft 115mm Jet

Thanks to this Forum I have successfully acquired and installed a 150cc Flat Top Piston Big bore kit. I have uprated the Main Jet to 115mm and put on a L230 Camshaft. Key observations were:-

1. Take care with the Mikuni Carburetter Gasket as once removed is difficult to return.
2. The Camchain Tensioner, this needs to be retracted before refitting (obvious when you know how)
3. Do not lose the Camshaft C Ring as this is what it sits on when removing it
4. The L230 Camshaft doesn't have the end part to drive the rev counter cable - I am doing without
5. Remember that the Camshaft needs to have the oil holes at the top with all the flat parts at the top (I got this wrong initially)
6. Not all of the rocker head bolts need to come off, 2 of them hold down the rockers themselves and have not part in securing the rocker cover.
7. The SFM uses a K157FMI engine with a flat headed piston
8. I declared my upgrade to 149cc (even though its says 125cc) and it increased by premium from 140 to 200GBP - not an issue for me
9. I increased the sprocket size from 13 to 16 teeth
10. I replaced the small bulb in the headlight for an LED type light without an loss in performance - great for day running
11. When re-assembling I used black gasket sealent on the rocker cover, the barrel and head had supplied gasgets
12. Piston rings, top ring is the chrome one, second is the black one, the 3rd and 4th are the serated rings
13. Check the piston is facing the right way - the indentations are slightly different in size (check the diagrams)

I purchased the big bore kit that is marked 124cc with Big Fin - used Zarmark as the broker, but they have ceased trading as of December 2014 - the shipping was about 50USD so keep an eye on this as the weight is 2KG.

http://world.taobao.com/item/1369688...?fromSite=main


UPDATE
1. Will pull to 70mph (indicated) in 4th but fifth too long so going to try out a 15 Tooth Sprocket
2. Need to do a plug test as sense it is running too rich as starts on half choke and slow to come off the revs
3. Overall very good pull on midrange - have done 80 miles so keeping the revs down still!


UPDATE 14JAN

1. Went for a 14 Tooth Sprocket and this now pulls to 65 in fourth and will hold 70 in 5th with slow acceleration. Key thing is that it will pull into the west wind in fifth at 65. I am 90KG so this is also a factor.

2.-Changed the spark plug for a NGK CR8EIX the manual states D8RTC (but this one fits) - what was on there was a CR7E which is a hotter plug - I went by the LEXMOTO spec for SFM Roadster 8-A - Halfords 10mm Spark Spanner did the job (this is very hard to work out ) will post a seperate item.
-The spark plug that came off was worn but light brown so no issue with the mixture on a 115 Jet and L230 Cam!

UPDATE FEB16

1. It was running rich because the carb rubber was loose!
2. Now run in after 500miles. This will pull 70mph (displayed ) on the flat and will clock now at 80 on hills and tailwind. The 14tooth front sprocket I stayed with but I am 95KG so maybe could increase if you are lighter.
3. Changed the oil - 850mm required - says next to the filler cap what is required.
4. Slight hiccup mid throttle so may up the Pilot Jet to 40. (no longer issue !)

UPDATE April

Avon Tyre on rear after third puncture - much better handling!!!


UPDATE JULY - Fuel Tank leaking at tap join
Replaced and padding put under tank as vibration is causing the tap /tank connection to crack - on my third tank now

UPDATE 25 AUGUST 2016 - Exhaust

1. Stainless steel exhaust blowing at join. Drilled out rivets using 5mm drill but this is sealed unit, so took this to a local welding place to cut the tailpipe off so I can use the downpipe still - Stainless Steel is harder to cut and you need a good jigsaw blade if you are DIY (I couldn't be bothered)
2. Purchase a Revus Megaphone Exhaust Muffler Amazon https://www.amazon.co.uk/gp/product/...?ie=UTF8&psc=1 (this is actually from chttp://www.classicbikeshop.co.uk/ )
3. The exhaust is shipped with 3 reducing parts, but I did need to wrap some aluminium tape round the 40mm end of the downpipe and then PTFE Tape for gas (yes plumbing tape!!) to make the piple slightly fatter and also to seal the join.- my research shows that this is a good practice for " Slide on Mufflers "
4. This is noisy, I am no longer a quiet mototcyclist - will update whether it gets any MOT issues or feedback from other places!
5. It is noisy and ends around the back axle, some may prefer a longer muffler as this sis a roadster
6. No plans to rejet at the moment - but will do a plug test in a few days

Exhaust needed a muffler to get through the MOT.

UPDATE December 2016 - bike now done 13500KMs - 6000 on big bore kit

Replaced chain and sprockets.

Before the change
14 Teeth Front-41 Teeth Rear- 121 Link Chain (ratio 2.9:1)

Purchased
15 Teeth Fronnt-45 Teeth Rear -Chain 124 link D.I.D Heavy Duty 428 pitch (ration 3:1)

This has a geared the bike down slightly and made it pull stronger up to 65. Before this, 5th gear was a bit of an overdrive before with no pull. I do prefer it.

Top speed is still 70mph(indicated)





APPENDIX
Additional gaskets - http://www.ebay.com/itm/Gasket-Kit-f...3D171692343676


Really useful thread on this also - http://www.mychinamoto.com/forums/sh...ore-kit-fitted

Torque Settings for head bolts (M8 12mm) 20 NM (MAX) change the head bolts if you get the opportunity anyway
Torque Settings for Rocker Cover (M6 10mm) 10NM (MAX)

If you drop the camchain into the engine, a tent peg is very good for getting it out - all is not lost!!!!

I had a slight oil leak due undertightenin get the head bolts - I have an issue with bolt snapping until I had mastered by torque wrench - you have to be gentle otherwise you don't feel the click.

If you find the exhaust popping on the overrun, check the vacuum pipe from the carb is connected - I had knocked mine off during the tank removal (it connects to the unit under the tank). From my research, exhaust popping is due to air in the exhaust system. I am currenly researching how this vacuum system works as the Haynes manual is vague and I have unexplained pipes from the Mikuni Carb and from the crank case.

UPDATE AUG2017
17000KM, 11000KM on big bore kit, I tend not do more than 60mph so don't strain the engine, may explain longevity.

Still going, slight oil leak maybe from gearchange so ordered new rotorary shaft gaske based on research will let you know
http://www.ebay.co.uk/itm/131671619194

Ordered side panels for Lexmoto Street DFE125 as SFM125 panels out of stock, hopefully the same.

Fitted LED indicators, needed new relay.

Topped up battery with De-ionised water and starter motor started functiioning properly again!

DR Bike heated handgrips still working after 2 years

This bike is not giving up, so my excuse for an upgrade hasn't arisen!

Update

It was running rich because the carb rubber was loose!

Now run in after 500miles. This will pull 70mph (displayed ) on the flat and will clock now at 80 on hills and tailwind. The 14tooth front sprocket I stayed with but I am 95KG so maybe could increase if you are lighter.

Changed the oil - 850mm required - says next to the filler cap what is required.

Slight hiccup mid throttle so may up the Pilot Jet to 40.

Shame no way to vote users on here as I'm sure this post would be useful to many, nice to see the upgrade all went well and thanks for taking the time to post the installation procedures.

BBK vs QJ157FMI-2b http://fanyi.baidu.com/transpage?que...e=url&render=1
Failed ... c/r too high & stock con rod weight too light

Was this an overhead cam or pushrod motor ?

Quote:

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Originally Posted by NZBrakelathes

Was this an overhead cam or pushrod motor ?

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This is an overhead cam engine