Here is a copy of the the original post on the homemade Air Fuel mixture gauge.Its posted under the Great (& low $) Fuel/Air Mixture System For Top Tuning in Projects you're working on. I bought the same cheap "Dragon" gauge as RCQ92130 shows below from Ebay, and a brand new Bosch NARROW band O2 sensor off Ebay (I can post part # & price later) and a bung. From my research the narrow band sensors are listed for older cars from the 80's. Newer stuff runs wideband. It took me a while to find a part # for a cheap option. I welded the bung into my stock GY6 150cc muffler, in the muffler section close to the engine end where the head pipe enters. The gauge wont read anything when I start up, but once I'm running for a bit it starts working. I haven't messed with it much, but its kind of chintzy. The sensor I used is Bosch quality so I think the gauge is at fault - or maybe its the packing and baffling inside my stock muffler messing up the readings / flow???. Anyway Dan's right about buying a proper aftermarket kit to get accurate measurement, but I can't understand why the kits are still so expensive. Anyway that's my 2 cents.
Here's the post for the homemade setup posted by another member (RCQ92130): So here is a VERY low cost yet VERY good system anyone can add.
COST: O2 Sensor ...... $ FREE (see below)O2 Sensor Bung ..... $2.95 includes shippingWelding bung to Muffler ...... ?? (cost me $10)Wiring ........ $ more or less freeGauge ....... $12.19 includes shippingTOTAL: $25.19 plus the wireBung: http://www.ebay.com/itm/160855809633?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT Sensor: http://www.ebay.com/itm/171914557669?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT How it works: The O2 sensor sits in the muffler and reacts to the oxygen content of the exhaust gas. The output of the sensor is a voltage .... 0.2 volts is a very lean condition, 0.8 volts very rich. A perfect combustion gives about 0.45 volts. So, all you need do is read the voltage of the sensor to know exactly how your carburetor is set up. You can actually do this with a simply voltmeter ... but with a nice, fancy gauge only costing $12 it's silly to not get one that interprets the output for you and tells you "lean" or "rich" instead of raw voltage. O2 Sensor: Use an old (no good) sensor from your car; it will probably be fine. In your car the computer corrects the injector duty cycle every 10th of a second or so, using the output of the O2 sensor to know if to inject more or less fuel. Thus, the O2 sensor must react QUICKLY to changes ... and over time loses it's ability to do so and your car will not pass smog. In our scooter we do not care about this reaction speed - an O2 sensor that reacts in a 1/2 second, or even a second, is fine. So - keep your rejected car O2 sensor (or get one from a junk yard) ... as long as the heater circuit is not shot the thing will be fine. Note: do NOT use a "wideband" sensor as it's output is different and cheap gauges will not interpret the output correctly.
Wiring: There are TWO circuits in the O2 sensor: a heater and the circuit for output voltage. The heater circuit just needs to be wired to +12v and ground when the key is on. The sensor output just needs to be wired to the gauge input and ground. So, really only 3 wires: +12v (ignition); sensor-to-gauge; common ground for the heater and sensor output. The gauge similarly needs to be powered by +12v and ground, and have it's sensor input wire hooked up to the O2 sensor output voltage wire. Simple. Here is a short video of it showing air/fuel mixture as the throttle is opened and closed. It shows I have a VERRRY lean idle setup, and a slightly rich main jet setup: View My Video (who knows why TinyPic flipped the video upside down. The file below does not have this problem) IMG_0630.MOV Edited 19 Nov 2015 by RCQ92130
Thanks Dan and Cyborg. I started out the rebuild with lots of momentum, then life got in the way and the project just sat collecting dust. Felt great to hear it run and drive it. Last night was the 3rd run with the buggy. Before we went out I changed the oil again. This time it drained out nice and clean, with no fine metallic particles so the break in procedure worked well. Last night the kids and I drove around the house for an hour. Great fun. Here's a photo showing the kids sitting in the buggy, and a shot of the passenger side and rear view of the motor. Hard to take a good photo of the engine when its installed into the frame. Ignore the rats nest wiring in the photos, that one of my my next projects for another topic listing, along with a gauge install & upgraded lighting. I'm done with this topic unless anyone wants any help or suggestions. Thanks again for everyone's forum advice, and a special shout out to Dan Martin and his shop for selling excellent parts, offering excellent tech advice, and posting those awesome Youtube repair videos.
Hey everyone, I'm still alive and so is the project buggy! I've been crazy busy at work and going to my kids sports events. So busy in fact that I have not posted my progress. So I left off with assembling the gearbox. Then I reinstalled all the plastic shrouds, the fan, the variator, the clutch. Yes, for now I just put the stock variator and clutch back on to see the difference the BBK made. I just cleaned up those parts with hot soapy water and reinstalled onto the engine with a fresh cover gasket and the stock cleaned cover. Then i installed the engine back into the buggy a frame. Then it sat for a few weeks. Last weekend got to fill the oil and gear box. Used 15w40 Havoline conventional car engine oil in the engine and Royal Purple synthetic gear oil in the gearbox. The internal reverse was previously packed with synthetic grease during assembly, but from my teardown photos it appears there may be a hole that allows gear oil to pass from gearbox to reverse assembly gearbox. I'm not sure, but since I greased the reverse I'm covered anyway. Installed the original but new carb and redneck air intake, Connected all the electrical, hooked up a charged battery, filled the gas with Supreme, and pushed the buggy out into the driveway. The starter motor barely turned over the engine on the first try. Was getting worried I would need a heavy duty starter! Second try it turned over better. 3rd try she fired up! I feathered the gas pedal and she stayed running! No nasty sounds or any leaks so I started driving around the house. There are 2 options on break in. Do it gently, or run hard immediately for 20 minutes. I ran it hard to ensure good ring seating on the theory that the rings need need alot of pressure on them during break in from combustion process to keep them spread out and therefore scraping into the cylinder walls with pressure to establish seating of the rings and a good ring wear pattern. Seemed to work for me in this case! No blue smoke, lots of power and increasing power over the 20 minute run. Then I shut down and changed the oil. Found small amount of fine metal particles, as I expected from a total rebuild. Ran again for 20 minutes hard, then shut off for a 8 minute cool down. Then drove around briskly with my 10yr old son driving. This engine runs beautifully and the buggy is a lot faster than before! I will try to post some pics tonight to close out this post. The next project is to build a dash plate and install a tach, oil temp, and EGT gauges on this buggy, and modify the stock exhaust (gut it). I will start a new post for those.
So work is still crazy nuts, but with the spring here I just gotta get the buggy back together! I've spent a few hours last night working on the internal reverse gearbox assembly that my Baja Reaction 150 buggy came stock from the factory with. If you've followed along with this buildup you already know this GY6 150cc left side case is a rare bird due to the integrated reverse gearbox. The case is formed and machined totally different from the scooter left side cases (IF ANYONE HAS ONE FOR SALE MESSAGE ME). So any buggy owners with this setup will be interested in this part: Started out last night by cleaning all my parts thoroughly in preparation for assembly. There was a paper gasket between the engine case and the reverse gear housing, so I bought some automotive gasket paper from an engine repair shop (you can find it online too) 12" x 12". I took the dowel pins out of the gear housing and carefully laid the housing flange on the photocopier and copied it. Then I cut out that picture, traced it onto the gasket paper and cut it using scissors and a utility knife. Took about 30 minutes to make including a lot of test fitting. Then I coated this gasket with Permatex Copper Gasket spray, and let it dry for a few minutes. I installed the gears, springs and actuating levers using photos from the tear down stage to make sure everything was lined up and oriented correctly. Greased everything with synthetic grease. Installed the parts, set the home made gasket, and installed the gear housing. Had to rotate the output shaft a little and the gearbox slid right on and against the engine housing like it did from the factory. Installed the bolts using blue Permatex threadlocker. Here are 2 pics of the gearbox showing the installed internal gears, and 1 pic of the housing installed. Take note that I spent some time with a stainless steel wire brush from a welding supply store, and some brake cleaner to clean up the exterior of the housing. It cleaned up really well. Once the whole engine is assembled I'm going to go over the engine this way to clan it a little better before I install it. I wasn't going to get this fussy for a buggy build (its not a show car), but its fast an easy so why not.
Spent part of the afternoon Saturday assembling the top end. First I washed the new cylinder in hot soapy water, then wiped dry and oiled the cylinder walls with motor oil. Checked and gapped the rings (they were not pre-gapped) to .010" based on my 61mm BBK.Copper sprayed the gaskets, set the case to cylinder basket, and slid on the cylinder jug. Installed the lower chain guide into the notches in the cylinder. Copper sprayed the head gasket and set it into place. I had a mint stock cylinder head from the parts engine I bought (read above), so I cleaned it up and installed it with its stock cam. Will upgrade at some point when engine is broke in.
Its been its at work but I finally found some time to start re-assembling the case. Froze the crank in the freezer and heated the race in the left side case using a heat gun like Dan Martin recommends. Set the timing chain in place. Dropped in nicely. Sprayed the new gasket with Permatex copper gasket sealer spray - great stuff! Easy and holds the gasket in place on the case. Heated the race on the right side case and slid that over the crank bearing no problem. Installed the head bolts - had to look at some of Dan Martins Youtube videos to make sure I installed them correctly. Got it! Installed the oil pump, pump cover, starter clutch and starter gears. Doing more tonight.
So once the left case was welded it was time to assemble a complete block and get it bored to accept the 61mm BBK kit. you've been following along my case is now frankenstiened from 2 different engines. The left case is my Baja buggies original, the right side and timing cover are reconditioned stock used parts from Dan Martin. I bolted the parts together using the old gaskets. The right side was already bored, so my machinist buddy Peter bored the right side to match. He was careful not to take any material off the right to ensure the oil port wasn't cut into. 1st photo shows cases bolted before machining, 2nd shows after machining. Test fit proved the new BBK cylinder fits now. Time to clean and reassemble the engine.
Stripped the parts engine today. It is in beautiful condition internally. Spotless, and the top of the piston and combustion chamber looked were nearly spotless as well. Looks like it didn't see much run time. The case had broken engine mount tabs so it looks like it was in an accident when new then replaced by the dealer. Anyway great news for me for a change. Here' a pic of the parts engine.
Tonight I also finished stripping the last pieces of the internal reverse gearbox off my original Baja buggy left side case. Taking it to my buddy tomorrow to see if he can weld up that hairline crack on the underside. I'll post the results tomorrow night. This week the goal is to get crack welded, bore it at machine shop for the 61mm BBK, clean and bead blast the case, have the case ready for assembly this weekend. Stay tuned!
Here's a pic of that 150cc GY6 parts engine I scored on the weekend. Using this for its crankshaft and head, but keeping everything else for spare. Too bad the aluminum ears for the engine mounts are busted off as that case was looking pretty clean.
Ok so tonight I was able to remove both new seals and 2 of the 3 new bearings from the scooter left side case I bought from Dan Martin. I carefully tapped out the seals with a socket an hammer no problem, no damage. I carefully tapped out the axle bearing, no prob or damage. I pulled out the 2nd bearing by grinding down a machine screws head flat and thin, then inserting the head down into the bearing and hooking it it in underneath the bearing, then clamped vice grips to the bolt and tapped on the vice grips handle with a hammer. Popped that bearing out no prob, no damage. Found that trick on Youtube last night. The 3rd bearing needs a different approach as its not budging, I didn't want to push my luck so tomorrow I'll try the heat gun method Dan explained above. 1st pic shows new-used left side scooter case with the new seals and bearings before I started, 2nd pic shows same case with only the last pesky bearing left to remove. So far so good.
Thanks for the great info Dan. I have a brand new heat gun, so definitely using that. After I posted I watched some Youtube videos last night for tips, including your bearing/seal/bushing install to judge how much force it took to press them in & if you applied any loctite etc to them. Looks simple, just need to be careful. If I crack my "rare" engine case I'll be into some major costs (would have to build your scooter case and buy the external gearbox & misc parts for setting up a buggy reverse gear setup). Trying it tonight and will post results.