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Discussion Starter · #1 ·
I am under the impression that i can cut the dome off the cateye cylinder and mill to desired height and add a cag style billet dome? am i correct? if so are there any tutorials or good links on any other details... cant find much on the cateye engine specifically..
 

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You can but its not easy......First Ill say that the cateye engine is the same basic engine as an X2/6/8 engine except for a couple items like engine case color,, e-starter and ignition coil

PBU sells a 2pc headkit but theyre pretty unreliable and the kit is pretty pricey.....

You wont find too many tutorials...Theres plenty of members with threads doing the chop though and doing it with or without the FullCircle Crank..Doing it with a FCC is a very advanced mod...

The reason there are no real threads is because Im the first to do the chop by hand without the use of a lathe or mill....Im also the first to do it with a Full circle crank modded w/piston ported crankrod mod and without...I made no threads on it because itll require a machinist type background to get the lip totally flat and accurately cut or money spent getting a machine shop to do the modifications needed..Some machine shops arent cheap..

I threw the option out there that the 2pc headkit can be done by hand when I was brainstorming with EPR a few years back but hate feeling responsible when other members wanting to attempt just rush to chop then they bust things,,overport things and do things so blind it costs alot of money replacing parts and alot of lost time...

It kind of frustrates me as much it must frustrate them.....They could of just bought the PBU kit and waited eternity to get it and they would of came out neck and neck on that deal....Itll be a sway on the vote on the stress level experienced throughout the ordeal though..

Members like EPR and Fabian7777 have learned quick and done the chop sucessfully...Some not so sucessful......

Tools needed,,,Hacksaw w/finetooth diamond blade,,beltsander,,handfiles,,oilstone,,12x12 totally flat n true marble tile from homedepot,,1000 grit sandpaper

I do my chops with a very fine diamond cut hacksaw...You cut halfway in,,flip the cylinder and cut the other half through............I cut the dome off up high so theres more of the dome left on the cylinder leaving the cylinder hole smaller than the cylinder itself on the initial cut

I set my cylinder without a basegasket and the tightest you should set your squish is .035"...Dont go any wider than .040"..Any tighter than .035" prepare to spend big on fuel.......:)..Im pretty sure you want to go methanol so squish should be set to .024"-.028" with a 17:1 dome..

This is the first chop engine...I had more pics but a harddrive crash corrupted them and a ton of vids..This engine was unfortunately stolen a couple years back aswell..



My 56 mph homemade stand-up scooter

 

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Discussion Starter · #3 ·
Im not an inexperieced builder... just new to these bikes... wanted to make sure that the head would indeed work... i have access to a mill etc to make sure its perfect... Any links to the head that you have used in this chop? i have seen a few on ebay but didnt have any feedback...
 

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Im not an inexperieced builder... just new to these bikes... wanted to make sure that the head would indeed work... i have access to a mill etc to make sure its perfect... Any links to the head that you have used in this chop? i have seen a few on ebay but didnt have any feedback...
The Cateyes looking pretty good so far.......Id build a OHV racing engine for that bike.........

Get the cylinder headkit that promises to make a 49cc a 52cc...The exhaust port is casted a lil bit higher plus the ports are alil more robust and will require port clean-up......

Youd get even better benefits if you used a 40mm piston and bored the cylinder to a 44mm bore...Reason being is the compression releif notch
 

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Discussion Starter · #6 ·
Yeah you mentioned that in my last pm... i could probably tig the slot back up and the rebore the cylinders i have... i have quite a few engines to choose from but i was trying to keep this project simple... i already have a larger project about halfway complete for him.... a jr. dragster with a kz1000 engine with auto airshifter etc... i have way too many projects...
 

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I cut my stock cylinder under the fifth fin down from the top and stayed into the fin. I used a 32th hacksaw and took my time and was very careful. There is no room for error.
 

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Saw a video on how to do this (forget where). Couple of things I remember from it that you might find important.
1. make sure the cylinder base is squared to the bore before cutting the top (they are almost never correct). 2. they simply bolted it to a lathe and milled the top off (slowly). Removing the fins first and then cutting to height.
All in all it looked like a fairly simple operation with the correct tools. Took a couple of hours to cut the top off, think they were trying to keep it as cool as possible.

Hugh
SDscooters
 

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Discussion Starter · #10 ·
I thought of the lathe as well i uave access aswell but its alot harder in my opinion to get it chucked square in a lathe than a mill... but thanks for the info... all is appreciated...
 

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I did almost all my work with hand tools, could of done the whole thing but it would take too long, and I have 10 bikes, so I don't have alot of time. I used my dremel, and my 8" bench grinder on the cylinder head ring on top, even surfaced everthing on my alum surface block. Jewellers files & wet & dry sandpaper did most of the work. First thing we do is drill out the bolt holes in the fins to 3/8".
It has a 19mm Walbro HDA223 carb I got a good deal on from Hugh at SDscooters
 

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Discussion Starter · #12 ·
Dont want to keep starting new threads but would removing all the fins completely on a cateye flywheel hurt the balance too much since on alcohol cooling is not an issue? I just removed the electric starter and cut the armature off the shaft to lighten the one side of the crank and want to lighten the other side as much as possible without killing the balance...
 

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Dont want to keep starting new threads but would removing all the fins completely on a cateye flywheel hurt the balance too much since on alcohol cooling is not an issue? I just removed the electric starter and cut the armature off the shaft to lighten the one side of the crank and want to lighten the other side as much as possible without killing the balance...

Theres only two reciprocating mass help points on the flywheel......You can bandsaw out the fins on both sides and leave the two counterweights.....Then you static balance the counterweights and add weight to the lighter side til its dead nuts zero....

Just FYI its way hard to truely balance a single cylinder 2 stroke engine so dont be so critical of losing balance.........Theyre not built balanced

With all my small 2 stroke engine build experiments and such I found the only way to get a 2 stroke piston ported engine as balanced as possible is to lighten key components like the piston and add a full circle crank....The full circle crank must be modded with the crankrod from the piston ported engine and the piston ported engine built with reeds added to increase the nastiness of power and lowend grunt...........

On piston ported engines I add 4 purge ports to the piston to eliminate the parachute effect and enhance revs aswell as to lighten...I also dremel out the sides of the piston sides below the pin aswell as dremel out the thick bridge castings in the piston underside to further lighten it...For your build Id start with a wiseco piston/ring set........

I even drill out the center of the piston pin to lighten it aswell so after all that work the engine will now be 20% out of balance due to the piston assembly,,piston rod and lower pin weight that still needs to reciprocate over being built 75% out of balance stock..
 

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Discussion Starter · #14 ·
Got alittle more progress done... new chain and brake cables are on and functional... stretch fully complete... the extra engine i was gonna install now, after i took all the covers off i realized its a 43cc head and piston are signifigantly smaller... but it has a pullstart with no electric starter section which i like and it had an aluminum clutch in it... so it had a few good donor parts...
 
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