Wangye issues poor low end power

hi gents

top end power is excellent , but it wont get there !


Minarelli engine

70cc Nakaru , technigas pipe , Mikuni carb opened out to 17.5 mm

running pre mix 35 - 1

just done compression test - 70psi

been through jets sizes 70 - 88

going to try needle adjustments on 88

checked choke is off

checked fuel float level, petcock is new

put new intake rubber on ,

carbon reeds have tiny gap ,


had a new piston after seizing ( not Nakaru )

thinking I need new barrel and piston

any ideas kindly received

 

a box of jets

 

Why did it seize? Sounds like jetting to me too...

 

thanks scuba for chipping in ,

I had oil pump issues wasn't using hardly any, hardly any smoke

hence the pre mix but possibly, maybe I should try the pump set up again , add a little oil to the tank see if its better

plug looked good colour though , although she did get hot quick ,

It was really fast on last build , 50mph revved geared out , 35 up hill

carb set up hasn't changed ,

I haven't had any problems seizing since pre mix but lost all the drive up to power band - Could be the new piston

I had it ridable earlier on a 88 main , with the needle low , not 100% but you could pull away ok

so i tried 86 mid needle and it was no good ,

refitted the 88 low and it was bad again grrrr

I'm nearer progress though

going to take the top off and check the rings tomorrow , something else wrong

been on it all day ..

regards

 

compression should be around 150 psi says 49cc scoot forum , have to wait for the parts ..

work begins on my NRG mc3 ax today

 

OK had another go today

took the top end off and matched the new pistons windows to the Nakaru old piston

as were a lot smaller ,

diy honed the bore which had some small scores so they all gone now ,

compression wasn't any better , maybe worse now

but is improving the more I run it ,

had the stator off to check seals , all ok ,

and found oil pump wasn't driving correctly that's why it seized , was loose so tightened and all good , I'm back on oil pump now

I had a good look at the carb , and the pilot jet hole into the carb seemed tiny , I have some micro drill bits and drilled the hole a bit bigger

my bottom end power is back , enough to pull out with confidence , Probably my pre mix wasn't getting though there ,

I drilled a pilot jet bigger but it made the bike run like it's on choke , but lucky I had a spare old carb to rob from , back on standard pilot jet

I had my carbon reed s out and have tried to make them close fully with little success , I didn't tighten them up so much and applied Loctite to the screws was better ,

but I'm getting misfiling in the exhaust , popping sound ,not every time , but I'm putting it down to that ,

going to have a look at them in a bit ,

either that or I'm over fuelling and mixtures backing in the pipe - 88 main jet

anyway I'm going to try the reeds again ,

hopefully I can ride enough to get a plug colour ,

but yey back riding 3 days work tho

 

Those rings are gone and its ran with not enough oil

 

Yes oil pump issue as said ,

nice one ,I didnt consider changing just the rings .. cheaper option

Will order a new set see if its better

Cheers Scuba

 

You’ll need a new piston as well it’s to badly scored

 

yes was thinking complete piston , only £13

its ridable , but wont hit powerband ,even down hill , i'm running a 72 jet ,

it really needed the pilot hole on the carb opening up , sorted the hesitation out,

I'm getting backfire , it's occasional but there , and loss of power

I'll keep riding till I can get a new BB kit , Its still improving the more I ride , I haven't had any seizures touch wood

Ill keep this cylinder as a back up

need to buy a reed block kit too I think ,

I might wait see if its the cylinder first


regards and thanks

 

If its running with either of those pistons then thats your whole problem.

 

But you fixed the oil pump?
Or premix?

 

New piston and barrel as scuba says that’s problerly your problem, those ones are trashed

 

Cheers gents .
Looking forward to getting full power

 

Let’s us know how it gos

 

it's back on the oil pump

 

I’d just run premix if your going to replace the piston and barrel and you've had problems with oil pump

 

My new Barrel and piston arrived ,


Smoothed of the sharp edges on ports , checked ring gap to 015

fitted on no dramas apart from the usual gudeon pin clips ..

Its running nice quiet engine wise , I repacked the tecnigas can and it's nice and quiet

the plug was a nice choc brown , and I haven't had any more seizures

looking forward to put some miles on it

hope the flat spot has gone , then I'm going to sell it

had a bit of a gut wrencher , which bike to keep

But Ive decided

im going to be riding an MC3 AC 70cc NRG ,

just got it going properly gotta get an MOT and a new petcock

recon its a better bet for my tuning project off topic tho