Pocket Bike Engine Project

[lowracer]

Ok, I was going nuts thinking there was a problem with my pocket bike engine for the past week cause I was getting an nasty noise at around 8000 rpms. The noise went away at WOT at or over 10,000 rpms. Today in the mail I received a 2nd Staton double bearing clutch driver unit for Pocket Bike Project #2. I checked it out for fit & finish & was amazed at how smooth & tight the new bearings are on the new unit compared to the old unit (sloppy) which I've had now for about a year. Just to test things out I installed the new driver & took it for a spin...Wow, no more noise...
I then took apart the old driver unit to find out the inside bearing was shot. So the noise was coming from my clutch driver & not my engine after all (thank goodness). I ordered up two new bearings on eBay lickity split & will install them as soon as the box arrives to get the 2nd Pocket Bike Engine Project bike back on the road...
-Lowracer-

 

[lowracer]

Bought a fuel filter & while installing it, wanted to raise my fuel tank a bit to have a better line between tank & carb & to get the tank up away from the engine heat. I cut a few pieces of 1/4" aluminum bar & got a few new stainless steel bolts & nylock nuts to better mount the tank. Heres a nice pic of the finished job.
-Lowracer-

 

[Cagiva4ever]

hi ! lowracer

i have now Race Clutch installed and ready for testings. w-d-key groove is made etc and as usual i have taken lotsa photos from all steps into my collection + measurements etc.

should i write all into this Topic as you have simular engine etc ? and maybe a intrest in same issue..

as if i do that, can i have help from you for a search of suitable springs to race clutch as Alternatives if it happens that softer springs are needed to gain best usable torq and drive.

im living in a finnish siperia in middle of jack**** nothing around.

im keeping my eyes open to find a machine(s) or whatever with simular springs. i havent seen any alternative spring rates for these Race clutches on ebay's.

i will start my Testing with lowest spring(s) pre-tension, which is roughly twice stiffy Vs. std Clutch.

bye
m

 

[lowracer]

Cag,

Might be better if you start a new thread for your clutch.

-Lowracer-

 

[lowracer]

Ok,
I finally got around to replacing the bottom head gasket on 'The Beast'. I ordered 3 copper gaskets from Pocketbikeparts.com for $1.99 ea & decided to use two of them for this project (a bit closer in thickness to the original paper gasket that blew). I had to remove the 3 pull start cover bolts, the 2 exhaust header bolts & the 4 head bolts. The cylinder came off fairly easy leaving a dangling piston on connecting rod. After inspecting everything & scraping the remaining paper gasket away, I installed the 2 copper gaskets without any sealant & lubed the inside if the cylinder & rings with some 2 stroke oil & reassembled everything adding a few more drops of Red Loctite on the 4 head bolts. She started right up & sounded tighter than ever. I took it for a short blast around the block & believe it sounds a bit quieter than before.
-Lowracer-

 

[lowracer]

Today was 'Spark Plug Wire Day'.
A few days ago I removed & replaced my stock Chinese A7TC spark plug with a compatible NGK C7HSA. I then removed a spark plug wire to inspect it & realized that the stock wire is a piece of carp. I went to a few retailers to find good quality 5mm cable & the only one I could find was a similar piece of junk @ a Chinese moped store. Then I stumbled into AutoZone & found a nice 7mm double ended cable that I felt would work well for both of my pocketbike engines simply by cutting it in half. I used an exacto knife to whittle away a small amount of material near the end to better fit into the 1/2" space the 5mm cable screws onto its post. Then I used a small piece of electrical tape wrapped clockwise to hold the cable onto the outer post area to prevent loosening.
After test driving both bikes with the new wires & plugs I can definitely tell there is a difference. The stock wires must have been having contact problems & I was experiencing sputtering & poor fuel economy.
Stock Chinese plug wires & plugs are junk & one of the 1st things I wish I had upgraded...(see pics...1st pic is stock wire)
-Lowracer-

 

[LS614]

Very nice I'm still super jealous of this build and will have to do something like it someday!

 

[lowracer]

Its running really nicely now after the few recent modifications. I decided to take it for a longer ride today to the beach and back & twice over a large bridge. This is the first hill climb I have taken it on since building it (its flat here). I also wanted to test out the fuel economy & promised myself I wouldnt do any WOT speed runs (ok...I did one or two).
The bridge which is challenging on a pedal-only bicycle was a breeze. This engine has so much power & easily can accelerate on the uphill. I estimated 40 mph uphill & not full throttle. I put .23 of a gallon & ran it 35 miles roundtrip with just a bit left in the tank. Most of the ride was ~40 mph but through the small beach towns, I putted along at 15-20 mph. Doing the math when I returned home gave me figures of close to 150 mpg's...wow!
I am very impressed with this setup. When easy on the throttle, it sips gas & is very economical, but when the need for speed arises, it will run like a banshee.
-Lowracer-

 

[NEAT TIMES]

Lowracer
You may have it covered if past posts, when you say two head gaskets ? Are you still using the big bore kit with separate head and cylinder? Was looking at you carb pic a couple posts back, did your motors come with the reed valves between the intake manifold`s and block? I need to look at my cag motors, they have a different intake setup, but need to look at my big bore engine, may be like yours. Am thinking you could just add the reed valves to your engines, supposed to give a big power boost, but also rumored to cause seal leaks???

Ron PS did you see on youtube the rc "air swimming fish" ? too funny!

 

[lowracer]

NeatTimes,
I used two copper base gaskets instead of one when I replaced the paper base gasket. The copper one is thinner than the paper one so I used two to keep compression from going up (its already high enough). It is the big bore kit w/ seperate shiny aluminum top head cap that the spark plug goes thru. The engine does have a reed block between the crankcase & intake. I am very happy with the output of these engines. I got two of them now & for a 6 lb powerplant, this thing to me is a wonderful app for a bicycle.
I am not a member of the 20 mph club! I can pedal my road bikes & maintain 20 mph avg speeds.
From reading forum posts, getting the correct gear reduction (this engine, or any engine) is a must & if you dont gear these to run in their sweet spot, the engine can feel like a dud. I did an experiment with a 1.75" engine pulley instead of my normal 1.5" to see how it would affect rpm's & top speed & the change was eye opening...
The engine never got into its powerband & felt anemic, like night & day.
I yanked the 1.75" off quickly...lol
Right now its at 15.6:1 & I measured it doing a rollout test (one wheel revolution with my weight on the bike : 15.6 engine pulley revolutions) & is working out real well for my type of riding.
I havent seen the you tube video of the fish yet?
Thanks
-Lowracer-

 

[turbojoe]

Hey lowracer,

How much torque did you use on the intake manifold bolts? I'm replacing the head bolts and I figured I would replace the intake bolts as well. Would it be the same as the head bolts? 8-10 ft-lbs?

 

[lowracer]

turbojoe,
My intake manifold came attached when I bought the engines. I checked the bolts to see if tey were loose & they were tight. I dont know the torque ratings but I got my headbolts tightened way more than 8-10 lbs. & they seem to be ok now (not loosening up anymore).
-Lowracer-

 

[turbojoe]

Well, actually I stripped out the socket heads on 2 of the head bolts on my engine despite going only to 10ft-lbs. I haven't been able to get off yet because the lack of tools, so I bought a second engine for $65. These are the 1 piece cylinders by the way. I thought I would put the carburetor from the first engine on the new engine since it's better. But since I'm having the crappiest luck with these, I wonder if I should use a different type of bolt as well?

 

[lowracer]

turbojoe,
You stripped the socket head & not the crankcase threads?
These use a 5mm metric hex wrench (not english).
Sure would be an easier fix if its just the socket head & not the crankcase threads.
-lowracer-

 

[concretepumper]

Hello lowracer, Can I ask where or how you made your front rim? I like the belt drive idea. I have only built a few FD's so far but my hardware store has tons of belts and pulleys.
That little motor is great! I had a pocket bike with the same motor. Great power for its size & weight.

 

[turbojoe]

Yes, it was the socket head, not the threads. If I can't get them out I'm sure I can find somebody that can.

 

[lowracer]

concretepumper,
Here is a link to my post about How to make the drive pulley.
How to make a V-belt drive sheave - MotoredBikes.com: Motorized Bicycle Forum
Cheers,
-Lowracer-

 

[gera229]

So did you guys have any problems with head bolts so far?
Did you have any problems at all over the time when you are riding it?

Or is it running strong now without any problems for a while?

How many miles are on your cag engines?
Are they both stage 2?
What is the most miles you have ridden in 1 day without stopping? Did you have any problems after or during?
What is your max speed?

Also since these engines are high compression and high RPM do the 6mm studs hold on well?
Aren't they supposed to use 8mm studs for these engines and do 8mm studs hold on better? They won't fit, but I'm just wondering.
For lower compression engines like China girls 6mm should be ideal, but for these engines with high compression and high RPM are 6mm too low or are they just fine?

How many miles is on your Subaru EHO35?
I noticed the Subaru engine is a 4 stroke engine, so it will be weaker and quiter as well as more reliable.

 

[lowracer]

So did you guys have any problems with head bolts so far?
Did you have any problems at all over the time when you are riding it?

Or is it running strong now without any problems for a while?

How many miles are on your cag engines?
Are they both stage 2?
What is the most miles you have ridden in 1 day without stopping? Did you have any problems after or during?
What is your max speed?

Also since these engines are high compression and high RPM do the 6mm studs hold on well?
Aren't they supposed to use 8mm studs for these engines and do 8mm studs hold on better? They won't fit, but I'm just wondering.
For lower compression engines like China girls 6mm should be ideal, but for these engines with high compression and high RPM are 6mm too low or are they just fine?

How many miles is on your Subaru EHO35?
I noticed the Subaru engine is a 4 stroke engine, so it will be weaker and quiter as well as more reliable.

Initially the headbolts were a problem getting loose until I swapped for longer bolts & used the red loctite. Since my cags are out front, I could hear weird sounds as my headbolts were getting loose. They are good to go now with around 1000 miles on them now. Both are Stage 2's & the most I rode them in one day non-stop was a full tanks worth to test out fuel economy (just under 1 liter of fuel got me 35 miles=152 mpg's) with no problems. Max speed is 55 mph & she pulls from a dead stop to 55 in speedy fashion. The Subaru Robin is a super reliable engine. I now have a few thousand miles on it with no issues whatsoever. Its slow compared to a Stage 2 cag, but it is quiet. I'm sure I could quiet down the cags with restrictive pipes but that kinda defeats the purpose of a 2 stroke. They were made to run on expansion chamber pipes & run they do....
I wish the headbolts that come on these cags were more stout. I'm not going to try modifying the case threads unless I strip one out. If I didnt go with the cag, I'd opt for a Morini but at much higher expense & harder to mount.
These cags are ideal for MB use & are very lightweight powerplants. So far both have been reliable & @ $129 w/free shipping, they fit the budget. Parts are very inexpensive & easy to find since pocket bikes are so popular...
-Lowracer-

 

[5-7HEAVEN]

Have you tried using an aftermarket Walbro carb on the pb engines?