Posts
609
Joined
7/24/2017
Location
Sunman, IN
US
Edited Date/Time
6/19/2019 8:19pm
Have a 17 ktm 150sx has full hgs exhaust , v-force 4 , 13/46 gearing and jetted for vp u4.4 race fuel bikes crisp . Looking to do full mod motor but looking to get head done first get the squish correct , my dads 17 ktm 150xcw had head done compression ratio is 17.5:1 is this too high or about right for this motor . Any help would be appreciated 
Fmf pipe did better than hgs on the dyno
I dont know what you ride but a 13/46 gearing is a
bit to much for MX Track
I ride 13/50
The Shop
About the Motortuning, i spoke with a German Engine Tuner in Dezember.
And he told me the 2016+ Models are so good from the Factory that you can only make 5% more Power
with a full Engine Modification.
On the 2011-2015 Bikes he can make 13-15% more Power.
So i save the Money and spend in good Suspension Service.
I've had bills and doma pipes on my old rm125 and they are great pipes. The hgs sounds like a top end screamer, probably gives up a little mid range to the fmf
Sproket 13/46
Power valve unscrewed at max.
37.5 pilot 540 main
Ride mainly in a sandy track and the bike ride awsome.
If you didnt try the 13 46 gearing. Try it before commenting badly about it. With the stock gearing i was cornering in 3rd and the 4th gear miss just a little to work too , lol goin with 13 49 or 50 you should cornering in 4 and get the 6 all out in the strech for sure.
But as for mods, I milled 1mm off of my 16 125 head surfaces and then set my piston height to 1mm below the top of the cylinder. This raises all port heights, which for a 150, is a good thing, as the cylinder castings between the 125 and the 150, are the same, but the bigger bore of the 58mm piston affects port heights by lowering them due to the larger bore removing more of the port area, lowering all port heights in comparison to a standard 125 bore. This little mod was cheap, and worked wonders in my 125, so I can imagine it would be even more benificial to do this to a 150, due to the displacement increase. Next up, steel clutch plates, there are 2 steel and 4 aluminum clutch drive discs, remove the 4 alu plates and swap them for steels, this will help the Clutch pack from slipping, my 125 at wide open, was slipping clutch, and simpley adding all steel clutch plates added a lot of top end speed, and I could feel the bike was way faster down the straits afterwards, plus steel clutch plates extend oil life by not contaminating it as quickly as alu plates will, as for exhausts, I had the fmf, and it wasn't really much better than stock, other than it helped to fill the the dip in the power curve, but I did feel my pro circuit works pipe and r304 woke the engine up waaaay better than the fmf did, but, I sold my 16 125 due to it being tooooo light for a 6' 180lb rider, had the suspension set up for my weight, and the bike was no slouch as Iv mainly owned smallbore 2 strokes most of my life, and can ride them like intended. These are no slouches when it comes to laying down some pow, but they need massaging, and to be honest your best interest, is to get rid of the stock Reed block as it's so flawed from the factory, like a purely bad design, I did try the v4 block in this, and felt it sealed up better but the reed stopped robbed a ton of top end power, and my modified stock block out flowed it up too easily, I never got the chance to run the radvalve, as I sold the bike before it was released to my disappointment, but Iv always gotten better results with rad valves over the vforce blocks, and Iv tried vforce on lots of the bikes Iv owned thru the years, yz125/250, both better with radvalve over vforce, cr250, radvalve blew the vforce
Out of the water easily, and on my 2012 250sx, the radvalve was hands down superior to the vforce. But if you were to choose I'd almost go with the 250sx radvalve over the 125, as the 150 could probably make use of the 250's extra room in the Reed block for better flow up top, same base plates between the two, as they come with the same Reed block from the factory for all ktm 2 strokes now (pretty lame :/ ).
Anyone looking for a 125/150 pro circuit exhaust??!?!!? Iv got one up fer salé, next to new condition
Pm if interested, give me your addy, and I'll get a quote on shipping and we can hammer out a price.
Crankshafts are dimensionally identical, as vhm states one part number for each other cranks, middle/high inertia, hot rods, the same, wiseco same, all of the 125/150 cranks are the same for 1999-2019.
So I'll get to my point, if all ktm did for the new crank is shave 2oz Off it, and if the piston gudgeon pin heights are the same between the 54/56/58mm pistons, then technically, (I don't know this for sure, but Iv done enough reading on this subject) but if the cylinder heights between the new 125 and 150 are the same, it should be possible to take an old generation 144/150 58m crankshaft, and litterally drop it into your existing cases with zero modifications, like direct bolt in, using oem parts if you so wish, with zero grinding involved, a literal bolt in stroker crank for the new 150's.... turning it into a 154cc engine.
Sorry for this, but you opened up Pandora's box with this topic, as I'm a severe fan of ktm smallbores, love them to death.
https://m.youtube.com/watch?v=llJ5jtf07BA
Pit Row
I use 6th
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