Nitropropane

[Fly1]

I,m a ole kart racer & have got a hoot from the thread. You bike guys are crude in how you tune these engines, & I just say that in a friendly way.
You guys are having a great time doing what you do & that's what it is all about. One thing though Karl you need to work on your welding (wink).
Karl what is your high speed & low speed needles set at from closed? You might look into getting a pop off gage to set that pumper carb. 12 LB
should be a good pop off pressure. You can adjust it with the fulcrum arm in the carb. Also pressure test your engine first before messing with the
carb. Pumper carbs work off crankcase pressure & if you have a air leak in the engine some where you will never get that carb tuned right. Pump
the air pressure to 12psi into the engine & spray the engine down with soap & water & look for bubbles coming out around seals gaskets ect. Hope I helped.

Fly

 

[Karl Snarl]

Shes been leak tested 3 timed. An yes Sir its a crude experiment. Lol. Just for fun. I dont remember off hand where im at on turns. Gonna change soon with the cr80 pipe im fabbing up. An as for my welding, its with a cheap fcaw, likes to lose ground or bind and studder, an its ac, wtf. Lol. I dont worry much because it will all be ground, blasted, sanded, filled, primed, and then painted. Now see my work with one of our millers at work, they are beautiful welds. An well im also being paid quite a bit to make them look good. At home tinkering i dont care to much.

I would love to hear your insight on this, any tips or tricks. Im not a douche, Im here to share as well as learn. Im not a dummy, been round motors my whole life etc. But i also know i dont know everything and am glad to hear from someone elses side. Few of these guys opened my eyes up to some new ways of building these bad boyz. Lol. This experiment is to get it right before i go support the MB community and buy the kit. Was going to make the spacer etc, but I felt the need to keep money flowing to the innovators of this hobby. More they make, more R&D, they can afford. Since they cost a pretty penny, I want to get all my mistakes out of the way on this steel sleeve jug, so i doing ruin and expensive scooter jug.

I,m a ole kart racer & have got a hoot from the thread. You bike guys are crude in how you tune these engines, & I just say that in a friendly way.
You guys are having a great time doing what you do & that's what it is all about. One thing though Karl you need to work on your welding (wink).
Karl what is your high speed & low speed needles set at from closed? You might look into getting a pop off gage to set that pumper carb. 12 LB
should be a good pop off pressure. You can adjust it with the fulcrum arm in the carb. Also pressure test your engine first before messing with the
carb. Pumper carbs work off crankcase pressure & if you have a air leak in the engine some where you will never get that carb tuned right. Pump
the air pressure to 12psi into the engine & spray the engine down with soap & water & look for bubbles coming out around seals gaskets ect. Hope I helped.

Fly

 

[Karl Snarl]

roller both top and bottom, a crowded would be better on the bottom for sure! 14.5:1 uncorrected is 10:1 corrected (roughly) that not too bad, Lambretta's calculator will give you exact compression figures very quickly,https://lambretta-images.com/tuningh/port-timing-calculators/

Ok corrected sounds more like it. I was wondering if i messed up my math, so i measured three times more and avg. So 10:1, i can handle that. Not to bad on the bearing.

 

[Street Ryderz]

Ok corrected sounds more like it. I was wondering if i messed up my math, so i measured three times more and avg. So 10:1, i can handle that. Not to bad on the bearing.

Still kinda high as you said and I would want a real good balance to have faith in them (even branded) but hey if your ready for it that long fishtailing skid can be ridden out, right ? LOL I 've had my share! Be safe man enjoy the ride.

 

[Karl Snarl]

Still kinda high as you said and I would want a real good balance to have faith in them (even branded) but hey if your ready for it that long fishtailing skid can be ridden out, right ? LOL I 've had my share! Be safe man enjoy the ride.

Oh I've had some fish tails in my day. Few of these bikes. These bikes at least aren't going 75 when it happens. lol. Only ht engine I totally destroyed (my fault, and I knew was pushing way past the safe limits) locked up at 42.9 mph, I was pushing for 43 at tht time. I rode it out, but it did tell me it was coming about 2 seconds before she locked. Heard, clink, chink, boom, smack, tinkle tinkle, scratch, scratch, then errrrrrrrrrrrrrrrrrttttttttttt of the tire. It locked so hard it bent the drop outs, slid the tire forward loosing the chain. The jamming it and seizing the piston at the same time. One of the reason I made the pipe so long was to keep the rpms down on this motor. I really don't want it spinning past 7k with the heavier piston. I just don't think a caged bearing on an unbalnced crank can handle all that force. I'm not trying to spend a whole lot more on this motor knowing I'm going to build a hybrid next year. Been drooling over the smolik website. lol. They seem to make some fine wares. Stuff I would be happy to spend on, if just to help keep a great company alive. I'm not trying to blow the motor, so I may put a bigger chamber on, head on. I just love how this cast head looks.

 

[Chainlube]

You can ease the pressure a bit with a head gasket.

 

[Karl Snarl]

You can ease the pressure a bit with a head gasket.

I think I'm going to have to put a head gasket back on. Using an industrial silicone rated to 800 degrees from work at the moment. Works out though, my M8 coupler nuts came in yesterday and I have to remove the nuts anyway to put them on. Might as well clean it up and toss a head gasket on while I'm changing the nuts.

 

[Karl Snarl]

Ok, got the pipe, need to fab it to fit. I have also bought a bigger saw carb to replace my hs254b. I think what I will do is get this experiment running perfect, then use all I learned on the minirelli jug kit I am going to get from smolik performance( they cost a pretty penny, so make my mistakes here instead of on the $265 jug kit). Reason I bought a bigger saw carb ( waiting for it to come in) was that I know the new pipe is most likely going to need more fuel. I'm right at the limits of this carbs ability to feed this engine. They work perfect for the 66's, but its stretching it for nitro and an 79cc jug. I got to looking and notice my high screw would self adjust it is so far out. I put a longer spring on the screw to stop its from walking. The carb I am upgrading to is about 2mm larger on venturi size. 17mm vs 19mm. I've been trying to find a 20-22mm one, but no luck so far. That research continues. On my 66's the venturi is perfect at 17mm for the way I port them. Lower end power for torque over max hp. I haven't got much time on ol' red this weekend. Spent the shop time mainly maintaining Green bean and Big Junky. New chains, bearings, cogs, brakes, etc. Stripping down Little junky today to trade a one piece 66 engine to a buddy for a split jug/head 50cc for a nephews bike I'm building. He thought he was getting a sweet deal on a 66, he didn't read. lol. He put the bike together and called it crap because it had no power. lol. I took 5 seconds looking at it to tell him why. lol. So he offered to buy Little Junky's motor for $100 bucks ( super low time on it), I countered with trade m your 50cc. He accepted the counter offer. Soon as the larger carb comes in, I'll be back to playing with Ol' Red.

If anyone can tell me a non walbro ( they cost way to f'n much) model number for a high low adjust pumper carb that has a 20-21mm ( 20-24mm is ok too) venturi, it would be great, lol.

 

[Karl Snarl]

Well I took ol' red out this weekend. She ran really good in the cool air, no ring ding ding idle down. She still don't like to idle with this nitro, i get about 20-30 seconds and have to blip her or she will fade out. I may have went a little over board on my porting. IT's now clear to me she's getting to hot for the nitro on 95+ days. Going to have to up the octane or retard the timing. I'm going to try retarding it a few degree's with the woodruff key. Then see how she behaves. I'm guessing she will totally lose the ring ding idle if I back her off 3-5 degree's. In my dream last night, I kept telling myself," she's running to advance ya moron, you need to back her off like when you build ya trucks. Don't be a dummy, the retard sits in the passenger seat." So lets see how that goes. I'm looking for a schematic to an adjustable cdi, I'd like to build my own. Just can't see paying that much for $3 in electronic parts, and 10 mins to solder up. Besides I probably got all the parts I need in my laser box to make one, just need the schematic now.

 

[Street Ryderz]

Well I took ol' red out this weekend. She ran really good in the cool air, no ring ding ding idle down. She still don't like to idle with this nitro, i get about 20-30 seconds and have to blip her or she will fade out. I may have went a little over board on my porting. IT's now clear to me she's getting to hot for the nitro on 95+ days. Going to have to up the octane or retard the timing. I'm going to try retarding it a few degree's with the woodruff key. Then see how she behaves. I'm guessing she will totally lose the ring ding idle if I back her off 3-5 degree's. In my dream last night, I kept telling myself," she's running to advance ya moron, you need to back her off like when you build ya trucks. Don't be a dummy, the retard sits in the passenger seat." So lets see how that goes. I'm looking for a schematic to an adjustable cdi, I'd like to build my own. Just can't see paying that much for $3 in electronic parts, and 10 mins to solder up. Besides I probably got all the parts I need in my laser box to make one, just need the schematic now.

5 degrees works well, as rpm climb unfortunately so does the advance. I've built a timing rig using an old bottom end, crank with no rod that has been statically balanced and the stock magneto. When this is spun up driving the clutch shaft I only need 2,500 rpm to get 10k at the crank being a 4:1 ratio and this is achieved easily just with a drill, then with spark strength tester attached along with two stroke timing light and a degree wheel attached to the crank shows me the advance or curve through out the rpm range. I making a video of this unit testing and showing the commonly used cdi's it's just a matter of finding the time. The adjustable cdi schematics that are out there like Jags still need some refining for high performance use, and if your good with electronics there are very good cheap options Like my current go to is using the super charged cdi that can be found for 20 bucks and I have it reworked at a cost of 15 bucks and the end results are base timing 15 degrees btdc rather than 20-25 and peak rpm is 15-18 rather than 28-32 mind you this is in conjunction of 4-5 degrees on the crank, this has been the most cost efficient way for me so far and people love it, helps smooth out the upper rpm range so it saves engines and rides better.