very hard to turn over & start (GT2B)

soup325

soup325

Member
Hi,

I got another problem with my grubee skyhawk GT2B.

Engine: 2 Stroke, 48cc. with NT carb and SBP shift kit.

The other day, I noticed my engine is very very hard to start (from cold) and down on power. Im suspecting that something has broken in the piston ring area. Im suspecting only one of the piston rings has broken, as i still have some compression for running. Thus creating a large amount of internal friction some where.

it still runs..........just.

The reason I think it is a piston ring is, I can take out the spark plug out and turn the engine over using my hands, turning the the pedals. Now, I have to hope on the bike and use my feet on the pedals, just to turn it over.

There is no binding of the drive chain I can find. As i can still pedal with the engine off and it still runs.

Am i on the right track??

I plan on pulling the jug off tomorrow. lucky these engines are like the trusty Lycoming or Continental engines I use to lend a hand on.
 
when i pulled the cylinder off, i found my liberal use of gasket sealer has clogged up my transfer ports and fouled the piston sides.

now, the fun job of picking off the brown loctite out of the ports and a very light sand of the piston, is needed.
 
update: I have ordered a new piston.

The gasket sealer that I have used, made it all the way around the internals of the engine.
even underneath the piston rings, and coated itself to the ring seats. this has caused the piston rings to push out and which is causing the piston rings to apply too much pressure to cylinder bore walls. which made starting and turning over the engine over so hard.
 
TakeiT said:
I cant turn my engine over without pedaling, and I got nearly 200km on it, I assumed it was normal.
Click to expand...

it's in reference to turning the motor over without the spark plug in.

for all the Australian rides,

if you need to order parts in a reasonable amount of time, DONT order from mbbimports.com.au < I can get parts from Perth to Canberra, on the other side of this country from screaming roo, sooner than this wog in sydney, will even post them. i ordered a piston kit on the 1st of June and still not even sent 6 days later.
 
Oh right, sorry. If your gasket was clogging the transfer port, then I would carefully examine the cylinder wall, make sure it isn't scratched. If it is, you should replace it.
 
Update - installed the new piston and only lasted about another half an hour till it seized.

bugger. pulled the jug off, hello...... the chrome bore has started to flake off the cylinder wall and naffed up my brand new piston. arrrrrrr

anyway, new piston, new jug, new bearings, new head studs, new head,

and new tools...an arbor press

looking forward to doing some engine rebuilding.
 
soup325 said:
I like to run a 100:1 mix with 98 octane. Oil : ELF HTX 909 fully syn, castor mix

http://www.wp-motorsport.co.uk/res/HTX-909_uk.pdf

After the first rebuild, I mixed a 75:1 mix for break in.

When completing the rebuild, I covered the piston and cylinder walls with a thin layer of 2 stroke oil during assemble.
Click to expand...
I read the specs on your ELF oil but I didn't see where it said to mix it at 100:1. It did say not to mix it with other lubricants.
Are you sure about that ratio of 100:1 with that oil?

Tom
 
the main reason why i didnt want to run it any leaner, was the potential of the castor oil to gum up the engine.

I have run this setup for around 40 engine hours/1200kms of riding, without any major engine issues.

The new piston I used was a higher tolerance piston with a ceramic coating on it. Im thinking it is a combination of new and old parts that had a cumulative effect of the problem/s.
 
I run Lucas semi-synthetic at 32 /1 , no smoke and no wear on parts. I just rebuilt my oldest engine that blew two crank seals due to a loose crank bearing, this engine has around 1500 miles on it. Other than replacing all bearings and seals all other parts were in good condition. I broke a ring removing them to check the end pins for tightness. New rings in the old cylinder and its running as good as ever.
 
I'm concerned with this piston. Where did you get it and is supposed to be used in a Chinese 2 stroke bike engine? That might be your problem. The ceramic coating might not be compatable with the plated cylinder walls.

Tom
 
Well, after about 500km of riding. the only problems i have had is the chain falling off.

new piston, ported jug, hi-comp head, skf bearings, exhaust, lockwiring, scwarble ebike tyres.

did about 300kms on the stock carb, then tuned my dellorto sha, done about 200kms or far.

primo!!

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