Pocket Bike Engine Project

[lowracer]

Cannonball2,
I spent part of the day reading all I could today about tuned pipes & expansion chambers & you're right.
Need some length of pipe before the expansion. Thinking back to my moped that went from 28-50mph just by adding the pipe, it did have some length before the chamber. Its stock pipe was very restrictive but allowed a decent takeoff. Once 'On the pipe' though all **** broke loose & it was truly amazing (nothing like the 1st time). I am ready for Tuesday to get here for the UPS man to bring me the goods...lol
-Lowracer-

 

[cannonball2]

Got my cap modded as per the Lowracer method and plan a bit more hands on later this evening.

 

[lowracer]

I received the pocketbike expansion chamber I ordered off eBay yesterday & installed it.
I had to cut a few inches off for clearance. I also wanted to see the difference between it & my homemade 1" flex pipe dual Ace Hardware Sausage muffler exhaust contraption. The pocketbike system is quieter and has slightly less performance. I think it is mainly due to the diameter of the pipes since the flex pipe is larger tubing & more free flowing (louder too). I am also guesssing that the large sausage muffler also acts like an expansion chamber & why the top end is so strong. The pocketpipe looks better & will keep my neighbors happier...
I may add the flex pipe to the expansion chamber to see if the added length adds performance without sacrificing noise.
-Lowracer-

 

[lowracer]

Ok, back to work in the garage some more on this new expansion pipe dilemma. I want to use the flex pipe for its length & the ID is larger than the pocketpipe. I cut some more off in small increments until I got it to where it has ground clearance & blows exhaust slightly away from the bike (& me). I also use part of the front tire to park in my garage us against the toolbox...lol
Here's what it looks like now & the performance is much better. It still is quieter than the original homemade exhaust.
-Lowracer-

 

[LS614]

I still love that bike and I'm still very jealous of you! Good job, looks amazing!

 

[killercanuck]

That looks whicked, thanks for all the pics and info you guys! Can't wait to read the difference when you get that aluminium stock

 

[lowracer]

More Pics

-Lowracer-

 

[lowracer]

Ok,
I dont think the Red Loctite is holding up too well. I noticed that sound again...You know, that sound of compression coming out of the engine. Very glad I have this engine mounted in front of me to see & hear all of its little sights & sounds.
I removed the suspect loose headbolt & inspected the threads. Threads looked good. I took it to the local Lowes hardware store to measure & its an M6 X 1.0 X 80mm cap bolt. Lowes doesnt carry long bolts, but McMaster Carr does & I ordered 10 @ 90mm's. I also ordered a bag of stainless steel split lock washers. I'm hoping that the extra bolt length finds threads inside the engine case, along with more Red Loctite, & the split lock washers will keep these bolts from vibrating loose. This engine is such an exciting screaming package that I have become quite fond of it & will order another if I can get a handle on the 'Mystery of the Loosening Headbolts'. At 'Ludicrous Speed' (Spaceball's) turning 10,000+ rpm's, something is gonna vibrate itself loose.
Will post my findings once all new items are installed.
-Lowracer-

 

[Cagiva4ever]

hi ! "lowracer"

what model/version Clutch (Friction shoes) are you using and with what kinda durability so far ? any issues or broken clutch shoe parts yet ?

i have Cag (40mm Diam piston) engine on my 26" mtb (chain drive, sprockets) and im using the STD 3-shoe clutch. done 100km so far and couple days ago all my 3 springs failed at same time on the Clutch.
( my clutch seller and clutch: ebay.co.uk/itm/Minimoto-Mini-Moto-Clutch-3-Shoe-FREE-SPRINGS-/270738263520?pt=UK_Motorcycle_Parts&hash=item3f09420de0 )

bye
m

 

[lowracer]

Cagiva4ever,
The 3 shoe clutch in my Big Motor Sport stage 2 (44mm) engine is the stock heavy duty clutch that they also sell seperately. I haven't had any trouble with it & really like the way it grabs. I use a Staton 78mm double bearing clutch drum housing which is pretty slick. I think if gearing is off (too tall), your clutch will be stressed & wear out quicker. I just did an experiment today by changing my engine pulley from a 1.5" (1.43" actual) to a 1.75" to see if I could get the engine rpm's down at higher speeds. It totally changed the way the bike felt (too tall). It made it tough for the engine to get 'on the pipe' & hurt performance all around. I'm thinking the clutch would have worn out if I kept it set up this way. I quickly switched back to the 1.5" pulley & called it a good $4.00 experiment...
Do a rollout test by putting your valve stem vertical @ the bottom position & mark the engine pulley (or cog). Roll the bike with weight on the bike & count how many times your engine pulley (or cog) spins around for one complete revolution of your rear wheel.
I used an online calculator to compute my gearing, but the rollout test is more accurate (& yes the results were different). My setup is 15.6:1 & I feel that it is the perfect for my engines powerband & flatland terrain. I do wish I had an overdrive gear for high speed/ high rpm reduction, but will have to be happy with what it is...
-Lowracer-

 

[lowracer]

Ok,
I received my new headbolts today & ran down to the hardware store on 'Wimpy' (EH035 powered rear friction drive bike) to pick up some lock washers. I have a bunch of lock washers on order that haven't arrived yet but for 17 cents for 8 of them, I would splurge to get this project rideable today.
I posted a pic of the stock M6 x 1.0 x 80mm bolt (black one) & the new M6 x 1.0 x 90mm bolt (blue one). With 2 lock washers on each bolt, & Red loctite on all the threads, I am hoping that it stays tight. The longer bolts definitely grab more threads in the engine case & hopefully the lock washers help prevent vibration loosening. I took it out for a few test runs & so far so good. It sounds like it is all nice & tight even at ludicrous revs. Time will tell...
If it holds up, I may have cured the woes that many people have using these Cag type engines (especially the higher compression head kit hop-up versions).
I really want to finish up another bike project that is ready for the engine to go on it, I just need to order up another engine & will get another of these once convinced the head bolts stay tight.
-Lowracer-

 

[cannonball2]

Watching with interest!

 

[Cagiva4ever]

hi ! "lowracer"

have you checked the 3 springs on your Clutch ? (does it look like the same as mine which i photo linked ?)

how many kilometres have you done so far with the Clutch shoe assy ?

on mine each of the 3 springs got little weak (streched like 1mm) after 50 driven kilometres and at 100km they all snapped (weak spring metal)
Its odd as shoes are still as Thick as New and Centrifugal opening of the Clutch isnt much when driving.

i havent calculated my Over all gearing but my gearing is short, i can pull wheelyes by throttle (5:1 reduction box. 10t & 44t sprockets. 26" rims/tyres)

(44t sprocket Diam 175mm. pitch 12,6mm. 415chain fits perfectly)


My next upgrade is to somehow find better springs or start using the Adjustable 2shoe clutch (no more snapping springs on it 4sure)
i havent yet thow noticed what springs would fit and from where, by looking PocketBike forums

 

[lowracer]

Cagiva4ever,
I haven't checked my springs (had it apart yesterday but didnt bother to inspect).
I have roughly 250 miles on my engine & clutch
The link you posted is expired & no picture available to view.
I would stick to the three shoe clutch for these engines (maybe just get a better quality mfgr or spring).
I also check the pocketbike forums & haven't heard of common clutch issues like you experienced.
Maybe your gearing is too short & puts strain?
I definitely cant pull a wheelie on engine power...(wow)
Check out ThatsDax website....he does alot of testing & has written about the three-shoe clutch & sells them.
-Alex-

 

[lowracer]

I pulled the trigger today on another engine, pipe, & expansion chamber purchase today for yet another MB project.
Here are a few pics of whats on order & will get a few more items to complete the job.
This will be the 2nd of the same engine (really love this motor).
I'll be swapping head bolts as soon as UPS delivers the engine.
The 90mm bolts with lock washers & red loctite seems to do the trick.
-Lowracer-

 

[cannonball2]

What are you building it on this time?

 

[lowracer]

Cannonball2,
Here's the bike the new stuff will be going on.
You've seen this frame before, once with a huge Lifan 2.5 on a rear rack, then on a front rack. It even has had a Subaru Robin on it for a short time. Now its looking like it will be similar to my other Pocket Bike Project bike only with no suspension, An aluminum rack & a 650c front wheel-to-wheel 'Lowracer Pulley'...lol
Enjoy the pics....more to come.
-Lowracer-

 

[lowracer]

Neat Times posted some interesting modifications to pocket bike clutch drum housings on this thread that I am interested in.
I want to remove the pinion screw that comes stock on the pocket bike drum housing & replace it with either a bolt or partially threaded 1/2" rod to allow me to mount my 1.5" V-pulley (1/2" bore). My question is how durable the single bearing is on these pocket bike drum housings?
I really like the Staton 1/2" double-bearing housing I got now, but dont want to spend the $69 + shipping on another one. I'll have this pocket bike housing on the engine I just ordered & would rather modify & use it, than selling it on eBay for $15.95 (like the last one)...
Any input is much appreciated.
-Lowracer-

 

[NEAT TIMES]

lowrider

After our pm`s , and a bit of thinking, if you could accurately drill the half inch hole in the clutch drum and find or modify a bolt head to clear clutch part`s and the crankshaft, Bolt it all together and weld bolt head to clutch drum. Would reccomend grade 5 nf thread bolt and grind a flat spot for the pulley set screw. Will check my inventory for the correct bearing number with 1/2" bore that fits in the bell housing. You will need shaft spacers to keep it from locking it with the housing. I did not know you would get the clutch unit with the motor. It should work imo.

Will also post shaft spacer part # also.

Internal lock star washer`s mite be good on the head bolts.

Using an allen head bolt may help holding it while tightning so the drum stays straight and not bent.

Ron

 

[lowracer]

Neat Times,
Thanks for all your input.
After seeing what you had done with your pocket bike clutch housings, it sparked interest in a DIY v-pulley driver for this project.
Engine w/ clutch housing should arrive this Wednesday.

-Lowracer-