Getting all 3 Horse Power out of your GT-5 Sky? (tear down)

recon chris

New Member
Apr 28, 2011
87
1
0
pacific grove
Are you getting all 3 Horse Power out of your china 2 stroke? I know I’m not. With the untrue rag joint sprocket, the “California Friendly” catalytic converter exhaust, CNS BS carb, unbalanced crank, Chinese bearings, and unmatched porting, I think I would be lucky to get half the rated horse power for the engine on a good day. So I’m changing all of that. Follow along and leave tips. I’ll also be making videos on how easy doing all this really is.
xct2
 

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,508
6
38
Ridin' inSane Diego, CA.
Maybe after this tutorial you can show us how to get all 2.5 Horse Power out of the HS 49cc 4-stroke. Just a thought for a future topic.......I've got a few tips for this one.

dnut
 

recon chris

New Member
Apr 28, 2011
87
1
0
pacific grove
Sorry pics are too big so youll have to click the link.
This is an engine i have already fully torn down and cleaned. It had about 400 miles on it. Im planing to put 2,100 more on it.

Crank disasembled and ready for balancing (also cleaned the rust off of them)
http://i1072.photobucket.com/albums/w364/reconchris/CIMG1189crop.jpg


Crank transfer port before port maching
http://i1072.photobucket.com/albums/w364/reconchris/CIMG1187.jpg

After
http://i1072.photobucket.com/albums/w364/reconchris/CIMG1188.jpg

Side by side before and after (not fine sanded yet just did it tonight)
http://i1072.photobucket.com/albums/w364/reconchris/CIMG1183.jpg

the perfect SKF replacment bearings (sealed for the cluch shaft, Sheilded on one side for crank shaft Ill explain why in the video i post)
http://i1072.photobucket.com/albums/w364/reconchris/CIMG1195.jpg
 

recon chris

New Member
Apr 28, 2011
87
1
0
pacific grove
These are the difference between the two bearings I’m using in the engine. One has a metal shield that doesn’t touch the inner raceway and the other has a plastic seal that presses against the outer and inner raceway keeping all dirt out.

http://i1072.photobucket.com/albums/w364/reconchris/CIMG1190.jpg

side by side
http://i1072.photobucket.com/albums/w364/reconchris/CIMG1191.jpg
http://i1072.photobucket.com/albums/w364/reconchris/CIMG1192.jpg

Somthing you should read before you tear down your engine
http://i1072.photobucket.com/albums/w364/reconchris/CIMG1194.jpg
 
Last edited:

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,508
6
38
Ridin' inSane Diego, CA.
Im going to stick to 2 strokes for this thread Scotto- but someone should post a thread for 4 stroke performance that is my next build :)

(pic soon on 4 stroke engine i have)
Here are a few pics of 4-stroke performance......


URL=http://imageshack.us/photo/my-images/827/img0994a.jpg/]
[/URL]

URL=http://imageshack.us/photo/my-images/535/img0978r.jpg/]
[/URL]

URL=http://imageshack.us/photo/my-images/213/img0754vy.jpg/]
[/URL]
 

dmb

Active Member
Dec 4, 2010
1,358
3
36
lakewood ca
lotsa room for big valves in their scotto, but too big will ruin botton end just like too big of two stroke ports can do the same thing. a happy medium is best for single speed motors. recon chris im looking to see how you unshroud the transfers, maybe relieving the piston crown?
 

recon chris

New Member
Apr 28, 2011
87
1
0
pacific grove
Some things I did today:

Polished the head (I had already tried it about 200 miles ago, so that is why the before shot doesn’t look so bad.)
Before
http://i1072.photobucket.com/albums/w364/reconchris/CIMG1236.jpg

After
http://i1072.photobucket.com/albums/w364/reconchris/CIMG1240.jpg

Opened up the transfer ports about 100%

Before sanding with material already removed
http://i1072.photobucket.com/albums/w364/reconchris/CIMG1213.jpg
After light sanding
http://i1072.photobucket.com/albums/w364/reconchris/CIMG1214.jpg

Corrected an odd casting defect that was left over from the factory. Im guessing every grumbie has this. It has to hamper performance by a good percentage if left uncorrected. I had to pull a Houdini to get a dermal bit in there without scratch the walls of the jug.

Before
http://i1072.photobucket.com/albums/w364/reconchris/CIMG1213.jpg
http://i1072.photobucket.com/albums/w364/reconchris/CIMG1219.jpg
After
http://i1072.photobucket.com/albums/w364/reconchris/CIMG1221.jpg
http://i1072.photobucket.com/albums/w364/reconchris/CIMG1218.jpg

Cleaned the carb up. Left the air filter off because I will be upgrading to a SBP low profile air filter (a million times cleaner and more efficient than stock sponge)

Before
http://i1072.photobucket.com/albums/w364/reconchris/CIMG1226.jpg
After
http://i1072.photobucket.com/albums/w364/reconchris/CIMG1249.jpg

And got a new Piston today (old one had one of its position pins vibrate loose, I stoped it before it killed the jug)
 

Attachments

Last edited:

recon chris

New Member
Apr 28, 2011
87
1
0
pacific grove
I have a question for you guys. How hot does the head on this engine get. Would it be ok to paint it with 500 degree engine paint or will it not be enough. I was searching on line and aparently there is such thing as 1200 degree engine paint. But i dont know were to get that stuf.
 

recon chris

New Member
Apr 28, 2011
87
1
0
pacific grove
Do you have to bake it on and what is ceramic about the paint? And does it dry Glossy and stay glossy after the engine has been run? I hate engines that have matt finishes.
 
Last edited:

dmb

Active Member
Dec 4, 2010
1,358
3
36
lakewood ca
hey recon chris first thank you for serving. what i was talking about is that the piston at BDC blocks the transfer ports exposing only part of the port sorta like a restrictor port. my worry is with a cut intake skirt and blocked transfers could put to much pressure in the botton end blowing the seals. maybe raising the port would work and the blocked lower part of the port would help cool the piston a little. by no means am i a two stroke engineer heck most of my spelling is wrong. please dont take my questions wrong im just a interested by stander. as far as paint cast iron stove paints work good on motors and exhaust pipes good luck dennis
 

recon chris

New Member
Apr 28, 2011
87
1
0
pacific grove
Well I'll look at the piston at BDC and if it needs the intake skirt mod im going to do it. Im not woried about the seals blowing out because of two reason.

1.The intake mod will not increas the pressure in the case by an extreem amount (maybe a few psi if im lucky)

2. Im replacing the seals with slightly thicker double liped oil seals from Motion Industries. (the originals are made from china and only have one lip ((even on the thick drive pinion gear side)))

When i set it up ill show you pictures

However were do you ge the cast iron paint and does it come in spray can form?
 

recon chris

New Member
Apr 28, 2011
87
1
0
pacific grove
Jimmy the one thing I have learned so far is to not baby this engine. And by all means dont be scared of it (coming from a guy who was scared to take it apart myself). Just tear it apart and replace the things that matter and make the mods that make sense to you.

The bigest benifit I think I will gain from all of this is knowing that ill have a bullet proof two stroke that wont break down, and if it does ill know exactly what might be wrong with it.
 

dmb

Active Member
Dec 4, 2010
1,358
3
36
lakewood ca
i think any home improvement store will have the paint. the piston mod is at TDC but BDC will show the blocked transfers. im surprised no one has welded a reed block to the bottom of these motors and blocked the intake port. reeds work very well on two strokers and you can use the complete up stroke for the air fuel charge. all your work looks very good to me and i'm sure your going to get the HP your looking for. dennis