Brother got SBP expansion chamber, less power now

Toadmund · Jun 29, 2012

My first suggestion is that his fuel line is kinked, it's almost in a 90Degree angle, but he won't hear of it.

Other than that, what could it be?
He suggested clutch slippage, we'll look into it.

Foaming gas? He has a new bike, new rubber mounts 2x thick as innertube.

Most likely problem?
Running too lean.

I myself have stock pipe, ported exhaust, ported exhaust pipe, ported intake pipe and notched intake on piston skirt. I'm blasting past him.

Could he be too lean?
Time to do some plug chopping methinks.

Whadda you guys think, anyone else have power loss after ex pipe add-on?

young grease monkey · Jun 29, 2012

yes, it is common to have a lean mix after installing the sbp pipe. mine had no power at all, then i drilled out the jet and it worked great.

Toadmund · Jun 29, 2012

Thanks, will sure look into that, I will have him read this post after work, it would be great to have other opinions for him to read and trouble shoot for when he gets home from work.
He should really join the forum, but he's just not big on forum posting.

It's Fixed.
He rose his needle and adjusted his clutch.

Thanks monkey.

young grease monkey · Jun 30, 2012

oh, and another tip. don't run it with a lean mix, it will damage the engine! i promise you, it is too lean. you can get jets from sbp. idk what size to get, maybe email them for a suggestion. it's always better to start too rich than too lean.

Greg58 · Jun 30, 2012

Lean is probably correct, if you look at the volume of a sbp expansion chamber compared to the stock muffler you can see why. Since the e chamber is less restrictive it purges the cylinder a little more.

ivan H · Jul 1, 2012

Also make sure the joins in the pipe r sealed well with the fiber reinforced silicon tubes. Leaks may cause problems with carb tuning. I cut up a tin can 2 wrap around, then used exhaust/muffler sealant b4 wrapping in tin & using hose clamps 2 make a sealed rigid joint. Solid mount the header, chamber & muffler 2 the frame so u dont get movenent induced leaks. Cheers

young grease monkey · Jul 1, 2012

what i did was get a longer piece of the silicon tube, 7/8ths, from sbp. it wasn't for performance, but there was a lot of oil coming out of the leaky joints and it made my frame and front of engine VERY dirty. as a bonus, you only need 2 hose clamps. makes a cleaner looking setup. ivan's way would work, too. many people use header wrap because it insulates and you can use it all over so the pipe doesn't burn you.

ivan H · Jul 1, 2012

Yeah, oil coming outta the header joins is kinda hot 2, so it's best 2 have it sealed. Its amazing how much can collect all over the front of the bike & motor in a short time if it aint. Cheers

Drewd · Jul 18, 2012

I sweated the copper fittings using lead/silver solder for the copper sections of the SBP tuned pipe exhaust. I also used the silicon hose as precaution and used crimp clamps (not hose clamps) commonly found on sprinkler systems to seal the houses securely. I still get some oil but its from that darn metal exhaust gasket which I feel is useless.

With respect to power and tuned pipe, too long of a header will mean power comes on early and engine may not rev as high as it had before and too short of pipe usually less low end torque but more power at higher rpms. There are many variables to take into account. My newest build was like your brother's, no power, but 7 hours of tinkering with different carbs (NT or Dax carb), jet settings, combinations with or without RSE reedvalve intake, several different header lengths, too many different ignition timing options, got me what I wanted: An engine with very good stump pulling power that revs easily.

ivan H · Jul 19, 2012

Hi Drewd, take that aluminium gasket & hold it over a lit candle 2 get a good all over covering of soot, then burn it in with a propane torch. Adding carbon like this will make it nice & soft so u'll get it 2 seal a lot better. Cheers

UBERKron · Aug 11, 2012

The soot has nothing to do with this. You are annealing the alloy. There is no high carbon aluminium. Do all you guys do meth or something? This is one of the most entertaining forums I know of. It should be renamed. " old fools that should buy a scooter but are too cheap" I've had six kits, all lasted one year. Each one wrecked two or three frames. I grew up and bought a motorcycle and a scooter. Here the cops don't mind gas bikes. I do. The vibration and very poor quality was like a self enforced jail term. Honestly life is too short for crap bikes. Get a scooter. I've put 8000km on mine only with adding fuel and oil.

Greg58 · Aug 11, 2012

To each his own " Young Fella" from one of the old guys.

ivan H · Aug 11, 2012

Ok, I'll bite. Firstly, I got 1st dirt bike @ 11yrs, started as diesel mech, MXbikes 14, road biles/hot cars 16 & have progressed thru more of each than I can count. Now I getting close 2 retiring age with deteriorating eyesight, hence these things. Now 2 the point, in another post as being an old fool I'm computer iliterate & post from phone..

ivan H · Aug 11, 2012

When hand forming sheet alloy b4 oxy welding into sports car body, it constantly work hardens, very quickly. Its is softened by the process of adding carbon, as described. Now I would think a softer gasket had more chance of sealing. Just bolting it in will start the work hardening process. Cheers, from an old fool

ivan H · Aug 11, 2012

BTW, I use a Hi Strength Steel frame with the motor tri angulated to it. Soon as I sort a tensioner for SBP shifter secondry chain it will b welded in. Vibration isnt an issue. A lotta things have reduced vibration, the last of reeding the motor & making it breathe thru 180 degrees, reduced vibration a lot, & it had already been reduced quite a bit. Cheers

young grease monkey · Aug 11, 2012

Enough bashing people's hobbies. I am done with the China 2 strokes, they do not perform well enough for me. If other people are happy with them, great. As far as the gasket, heating it up will do nothing. To soften it, you must get it to 900 f and hold it there for a few hours, then quench in cold water. This cools the metal fast enough that the alloying elements cannot precipitate out of solution and do not form long crystals. This makes the metal very soft. Aging will allow the alloying elements (particularly magnesium) to form longer crystals and the metal becomes harder and stronger. It happens naturally at room temp, but very slowly. Artificial aging can be done in an oven, around 350 f for a few hours works for many alloys. I would not try the heating-quenching without a kiln or heat treat oven, so this information is useless to most people.

young grease monkey · Aug 11, 2012

Maybe burning off the soot is a way to judge the temperature. The carbon certainly has nothing to do with metallurgy, aluminum can be directly melted using charcoal and no change to the chemistry of the metal. It picks up hydrogen gas from water in the air or from combustion when it is liquid, and this causes bubbles in the finished product. Heat and forming are the only things that will affect aluminum when solid.

dmb · Aug 11, 2012

wait a second is someone holding back on the meth? is it hidden in the cooking and chemical section? damm cant find my reading glasses i've been up all day and night ahhh!? their's a bug in my ear and the cop's are watching me through the T.V.!! now a more important message to all. sad to say i've heard these word's and more from friend's who were addicted to this killer and life ruining drug made by satan himself. once this drug grabs you theirs no escape. your be lucky to survive. and then theirs the children of the user's.. god help them because people seldom do. i've seen kid's being helped in the front while the parent is in the back steeling. i could go on forever but i'll get off the soapbox for now. thanks dennis

ivan H · Aug 11, 2012

Hi Youngreasemonkey, I dont doubt ur metalurgy knowledge, its obviously above mine & u were right when I ported the piston, which was a first 4 me, but it remaiins, wot was shown 2 me by wot I call an ol timer 2 anneal work hardened sheet alloy works, & a lotta panels were needed, a lotta bashing/annealling/bashing, well, hammering, not bashing but u get the pic, & my gasket dont leak. Cheers

young grease monkey · Aug 11, 2012

the old time tricks do work even if your instructor didn't explain why it works, not really important for sheet metal work. important to me cuz i cast and heat treat aluminum. i suppose that holding 900 for a few hours is the ideal situation for precise heat treating, your trick probably works almost as well. what did i say about porting pistons? oh, and copper gaskes work best. they are easy to anneal because they don't melt before red heat. get it to a nice bright red and quench. performance 2 strokes use copper head gaskets, never heard of aluminum gaskets being used in any engine besides china girls.

Brother got SBP expansion chamber, less power now

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