porting of SX150 barrel

[johnnyXS]

the jettex is a bit hit and miss in my experience but I know some people do ok by them with not sounding like a advert for Scootopia but their 22mm carb and their clubman are both excellent , the exhaust in general not only perfoms well (good rev's and mid range) but actually fits! good luck with the porting/upgrading . Paul

I do pretty much the same work on my jetex as Scootopia but I use original Dellorto in my carbs not an unbranded Atomiser with no specification like Scootopia do.
I wonder who makes Scootopias clubman ? Probably the same Indian Company that manufacture AF Rayspeeds clubman .

I already have bought the Rayspeed now so i'll go with that but it would be interesting to see if there was any real difference in low and middle range performance between the two.

Thanks for your input

[HxPaul]

I use a KBA clubman on both of my scooters and a jetex on one,a scootopia sh2/22 on the other,they both have Casa 185 kits on them,one is a series 2 and one is a series 3.They both run very well and I cant tell the difference between the jetex and the scootopia carb.By the way,the KBA clubman and the AF Rayspeed clubman are made in the same factory in India and are apparently exactly the same except they have different names on them.

[johnnyXS]

cheers paul thats what I assumed about the exhausts. I seem to remember reading somewhere that there was a lot of copying and skullduggery going on some time back re clubman exhaust manufacture in India . I believe the Indian Company chosen to manufacture the clubman exhausts for a British Company started to sell the exact same part (under an unbranded name ) into Europe for a lot less than the British Company who designed and commissioned them in the first place could sell them at.

If I could afford a Casa or some other 186 stage6+ kit i'd just bolt that on but until I win the Lottery or come into my Inheritance ....its going to have to be a simple bored out iron cylinder and piston kit .

i was hoping to find a member that had actually used a SX150 cylinder and bored it out to 175cc or 185cc and could give us the lowdown on whether stage 4 tuning porting etc was worth it or not but it looks like everybody goes the Ali cylinder 186cc kit route

I'm going to wait until I have the cylinder bored and fitted and see how the porting looks with the new piston and make my mind up whether to do some porting or not. I'll still match the inlet and exhaust ports to the manifolds of course.

Thanks for the feedback .

[CHRIS in MARGATE]

Lay base gasket over cylinder base and see if gasket or transfers need trimming. Lay prepared gasket over crankcase mouth and etch around the areas of metal that are proud. Relieve these with a burr and finish by polishing. Same for inlet manifold with gasket.
It's all easy metal to remove and not too invasive.

[johnnyXS]

its good idea Chris .

I'm very tempted to do all this porting malarky but the trouble is where do you stop ?
If i do the manifolds to cylinder matching and the transfer ports I might as well do the ports inside the cylinder as well .......its a slippery slope ....

I am really looking for a small capacity increase and some slight improvement in torque ( low to middle end grunt ) and most importantly a quick easy build .

I really don't want to end up with an engine thats tricky to tune ,keep on song ,carb spits back , difficult to start in bad weather etc etc and generally a bit of a pig to use like some can be.

I think if I was going to go to all the effort of a full stage 4 tune in terms of porting work on the cylinder piston and manifolds I'd wait until I could afford a 186cc cylinder kit and just bolt it on . So much easier and quicker to set up and tune and reliable power.

[EddieStone]

I have a stage four 175 and it goes very well. I run it with a 20mm SH1 through the air box and a KBA exhaust. The ports are slightly bigger than standard and it made a significant difference. I increased the front sprocket by one tooth and it'll hold 60mph on the flat.

The other thing I'd recommend is an electronic ignition kit. If you're running an Li crank, there's only so far you can go before you need to rebuild the bottom end with a GP crank.

[johnnyXS]

thats good info Eddie thanks. I've always wanted to have a long stroke 175 engine. I've never ridden one but I've always imagined they are a little less revvy and more suited to general hacking and cruisin about country lanes ..

I'll have to have another read through the Scootering article about Bang for Buck and also the Webster tuning guide too.If you say it makes a significant difference then i guess I should make the effort and time to do some mild porting
There is also an old tuning article around somewhere written by some Italian geezer whose name excapes me . Cos its all in Italian which doesn't help but the porting pictures are clear enough.

I'll buy a 16T front sprocket to try thanks for reminding me. I'll stick with thestandard series 3 Li150 gears for now .
Ultimately I intend to remove my 150cc engine from my LiS150 special and rebuild that so this engine is just a temporary spare to keep my only scoot on the road.

[dscscotty]

I've always wanted to have a long stroke 175 engine

you may be confusing conrod length with stroke? The TV 175 uses a 116mm conrod with a 30mm compression height piston, this is often confused as being a longer stroke,

[EddieStone]

thats good info Eddie thanks. I've always wanted to have a long stroke 175 engine. I've never ridden one but I've always imagined they are a little less revvy and more suited to general hacking and cruisin about country lanes ..

I'll have to have another read through the Scootering article about Bang for Buck and also the Webster tuning guide too.If you say it makes a significant difference then i guess I should make the effort and time to do some mild porting
There is also an old tuning article around somewhere written by some Italian geezer whose name excapes me . Cos its all in Italian which doesn't help but the porting pictures are clear enough.

I'll buy a 16T front sprocket to try thanks for reminding me. I'll stick with thestandard series 3 Li150 gears for now .
Ultimately I intend to remove my 150cc engine from my LiS150 special and rebuild that so this engine is just a tempoary spare to keep my only scoot on the road.

Yes, mine is the standard stroke length - it definitely has more low down oomph than when it was standard. Give Harry a call and ask what he can do for £100ish - he's a talkative chap but realistic. All tuners will persuade you to uprate the crank, but if you're on a budget it's not an option. If you're going to the trouble of dismantling it and boring it out, I would definitely get some work done on the ports.

[Kev Fox]

I had this little bit saved from Stuart Owens post regarding mods to his SX150.

simple really . I have an original sx 150 and the engine isnt to bad anyway . I polished the ports on my barrell and run through a delorto 22mm carb (italian only though) . I run through the air scoop with it fully cut out like gp and then through the air box but with no filter .Exhaust is a big bore and jetting is a 120 main jet . Gear box wise i ditched the sx150 as its hopeless . I run it on a pacemaker using 16/46 . As for speed it sits happy at 60 mph and still has a bit more left . It also runs on point ignition .Is it good ,well ive run the same set up for 17 years and done 20,000 miles on the same set up . Ive toured Europe on it several times and been all over Britain on it . It has never let me down once in all that time . Along with the fact it does 100 miles to the standard tank it is nice to drive as well . If you want big power then get a 200 lump ect . If you want a bit more use the original set up with these changes im sure you will like it .

[johnnyXS]

excellent post Kev thanks .
Detailed specification and personal experience of performance is worth a thousand guesses and assumptions.

[hullygully]

do it as a 175cc, get the porting & extra transfers (piston & barrel) done by Mick Abbey up in the Nth East, he's done my 175, a mates, my Gori 200, my TS1, a mates Monza & currently doin my Casa SS200

[Adam_Winstone]

This book maybe more suitable, it has good info of early stage tuning and cylinder conversions etc., its an easy read and although quite dated has good advice on simple performance gains.

Agree 100%

[Adam_Winstone]

"i was hoping to find a member that had actually used a SX150 cylinder and bored it out to 175cc or 185cc and could give us the lowdown on whether stage 4 tuning porting etc was worth it or not but it looks like everybody goes the Ali cylinder 186cc kit route"

... that'll be me then!

Before Milan 97 I had ported and set up a spare SX150 motor that was tuned to the spec' given in said performance tuning manual and thanks to my big end bearing giving up very few miles into the trip (about 30!), I ended up doing the rest of Milan and back (Lyon, Cannes, Savona, Milan, Turin, Aosta, back through central France) 2-up on said tuned 150 motor. The bike ran beautifully, toured at the going group speed and even out performed some of the bigger cc bikes (incl. 200) when taking twisty hilly sections, no small part thanks to running the original SX/GP150 gearing. This motor did my proud and performed very well for a 150.

Indeed, the bike performed so well that I decided to get more out of it after getting back to UK and bored it out to 175, then ran into issues with trying to dial it in again (jetting), then nipped up because of the quality of the 175 conversion piston, then eventually broke rings... all of which made me wish that I'd left it as a very good 150, rather than a poor 175.

Adam

[johnnyXS]

thank you for posting Adam, your story seems to mirror others experience with a standard 150cc engine including my own

I think I've decided not to do any special tuning and porting etc other than match the inlet and exhaust manifolds to the barrel.
I will get a quote for reboring to 64mm 185cc as I already have the piston kit.

I think the performance increase will come from the properly jetted 22mm Jetex and a 42mm Clubman with careful attention to the timing.