E50 first start, piston contact?

i promise im not a robot /

finished my E50 rebuild with a treats 50 kit and hi hi head. admittedly was getting very impatient at the end of reassembling it and started it up to hear the following:

Ive heard some kits rattle but I dont know what that sounds like - is that all this is or do I have a serious problem here? Definitely a metallic sound that keeps pace with RPM...I am leaning toward the latter. I installed a temp gauge with the kit which recommended to remove the crush washer on the plug. That combined with the hi comp head makes me think the increased depth of the plug into the cylinder is causing a no no even though i didnt notice anything when i turned it by hand. let it run for a while to warm up and begin the breakin process and took it for a short ride a few blocks varying throttle and staying at low rpm. when i got back the bike bogged out and died. restarted fine for a minute then bogged out again, wouldnt restart. went to check the plug to see what it looked like or if it fouled and it is now tight as fuck in the head and i busted my shitass harbor freight ratchet trying to loosen it. wont know the answer for sure till i go get a new ratchet worth using but just wanted to get a few opinions first. please be gentle. really trying to get this bike sorted so i can hit up a rally this coming weekend and im super bummed its not running right.

Re: E50 first start, piston contact?

matt boda1nz /

my wife's italkit for her nc50 sounds like that..

it sounds like it's slightly hitting on something, but it's not.

you gotta pull the plug and look, check your plug gap.

also, use a piece of solder, stick it in through the spark plug hole, use the kickstarter to crush the solder between the piston and the head to measure your squish. (edited)

Re: E50 first start, piston contact?

Overpriced Parts /

Did you set squish/compression? Base space so transfers are full open at bottom dead center?

Hi hi head has too much compression most times/sits too close to piston.

You need to hog out the head for better squish /compression and or space the base with thicker base gasket .

Treats sells 1.0, 1.5 mm gaskets and metal base spacers

Re: E50 first start, piston contact?

When you tighten a plug you really don't have to completely crush the washer so it should never be that tightn...you are going to strip theeeee threads like that...and always check the port height @BDC and deck height @TDC before assembly.....

Re: E50 first start, piston contact?

those treats kits do have a rattly clacky sound, but its pretty hard to say if you did or didn't fuck something else up that will cause it to grenade in a couple miles.

definitely take it easy on the spark plug, with the trailtech you only want to be about 1/4 turn past finger tight.

Re: E50 first start, piston contact?

speaks more of a junk tool then overtightened plug, but.

so many sob stories that hi-hi head brings.

if you didn't know why use a hi-hi before you bought it, you're condemmed to sieze.

stop, take a breath, read about squish for a few days.

then tear the top end down, and start over.

my money's on plug gap closed.

Re: E50 first start, piston contact?

Matt Mahloch -- MBM Customs /

Pull the plug out and turn it over by hand, does the piston feel like its hitting the head? Thats what it sounds like.

Some kits do rattle but that sounds excessive and more like a piston hitting the head thing.

Re: E50 first start, piston contact?

Sounds like piston rattle to me, most of them do it.

The more piston to cylinder clearance you have, the more noise you will have.

When you raise compression, they rattle more because of this clearance.

Replace the hi compression head with stock & note the difference.

Good luck.

Re: E50 first start, piston contact?

Yeah, I've got the same set-up, and I do not get anything similar to that sound, something is going on.

Re: E50 first start, piston contact?

i promise im not a robot /

update - pulled it apart last night and now I am even more confused, and sorry to the told-you-so dudes looking for carnage to disappoint...but everything looks fine. no markings on the piston, plug gap is still normal, no interaction between the head and piston along the outer edge near as i can tell either. very strange given how noisy this thing is/was. checked squish with some solder thru the plug hole and it barely even registers on two pieces twisted together, near as i can tell about 0.080" where it looks like the solder was barely nicked - which is much higher than i anticipated (and pretty much unreasonable) so maybe Im doing something wrong here to check it. I then reassembled, barely inched the plug past hand tight and started it, sounds much better but still has a bit of a weird rattle to it. related to the squish, the piston actually seems like it doesnt travel as far out of the cylinder as I expected at tdc - see last pic. this doesnt really address the noise issue at all but just something I thought was weird.

note im using the base and head gasket supplied with the kit, didnt do anything weird. maybe the kit isnt designed to actually work all that well together? guess i wont take things like that for granted anymore.


Re: E50 first start, piston contact?

i promise im not a robot /

anyway what i should have said was i dont know where to go from here, anyone have some suggestions on specific checks i should do at this point or any insight on wtf is up with my squish? thanks

Re: E50 first start, piston contact?

Brent Bublitz /

Get an air filter.

I had the same type of metallic pinging noise on my Puch. It was just exhaust noise from the chamber. Put your foot on the pipe, like a dampener and see if the sound changes or reduces. Some chambers can have a very pingy sound.

Re: E50 first start, piston contact?

try rubber fuel line wedged between the fins, glad the motor's ok.

wiki is sparse on squish

fun for some, MacDizzy says you can even set it to 0!

seriously, there is tons on the web to read.

Re: E50 first start, piston contact?


that piston is way below deck

fuck the hi-hi-head haters, those 50cc kits rip dicks with super high comp. I've run them 13:1 or higher.

i've seen a lot of them snag a piston ring, so check the ring gap, especially if it gets louder as the engine warms up. maybe go ahead and chamfer ports a bit more

could be that your crank is shot, hows the in-out play on the con rod?

uhhh... what else, i dunno. run it till it blows?

Re: E50 first start, piston contact?

i promise im not a robot /

ill try the air filter/fuel line in fins/better mount for my pipe since the tabs dont line up and see if that helps at all noise-wise.

ring gap looked OK when installed, and i did a light chamfer job on the ports but that said i may err on the side of really cleaning them up and take the jug off for some more work since i keep hearing these kits are snaggy

no in-out conrod play when i reassembled...no idea why the piston is so low at tdc. big ass squish means im just wasting a lot of fuel and leaving power on the table but what would i do? run no base gasket? shave something down? this seems to be the opposite problem of what people normally have. I have a 1hp crank, are they a shorter stroke or something?

other than that i guess ill just double check timing, break it in, get it jetted and rip it...see what happens.

Re: E50 first start, piston contact?

The most important thing to do is make sure the intake ports are fully open and the piston totally clears the exaust port at BDC....

Re: E50 first start, piston contact?

Matt Mahloch -- MBM Customs /

That piston needs to come up higher. Take a pic with the piston at BDC of inside so we can see the transfers and exhaust. How think is the base gasket, take a pic of that.

Re: E50 first start, piston contact?

i promise im not a robot /

popped the plug out and the head off - plug and BDC pics below, exh port is at the bottom in both pics, trying to show that and the transfer more than fully exposed - electrode seemed to be "chocolatey" but still definitely a little rich (this wasnt a WOT chop, just post moderate breakin ride ~10minn and i know its rich for breakin). i didnt take a picture of the base gasket but it isnt that thick, id say 1mm or less.

any ideas why my piston is sitting so low?? like i said it runs pretty decent, but turning it over by hand or kicking it i certainly wouldnt say its high compression as this head should make it, and i know it isnt (based on my huge squish)...how the hell do i increase squish by like 0.060" to get to the 0.020" neighborhood or less...run no base gasket? shave my jug down?? these are only partially serious questions. but seriously...?

also still no idea why this thing is so rattly but after holding onto the pipe and parts of the cylinder by hand to try to dampen any vibration last night if its some kind of resonance/determine if its some kind of internal contact, it got a little quieter but i still cant conclude what the noise is.


Re: E50 first start, piston contact?

yeah you'll have to ditch the base gasket, you can use kraft paper, grocery store bag works good, soaked in oil or even a thin smear of motoseal.

check that your booster ports in your piston aren't poking into the intake at BDC.. the TCCD comes pretty close on the 70 but i cant remember if the 50 is that close.

if it were me i'd probably run a countersunk head, and just correct the ports by porting the exhaust down to come even to the piston. it will be at least 60 bucks to get any machine shop to touch it for shaving down the base... if you have access or know someone

Re: E50 first start, piston contact?

crappy picture of a puch stock cyl i cut the base on a lathe.

piston is 1.5mm up from the head gasket.

tons to hate on in the process, but to justify:

my goal was to see what it took to add squish to a (junk) stock top end.

A35 mule.

disclaimer: this wasn't about port timing, abandoned once i saw how bad it was off.

piston 1.5mm up.JPG
stock squish 1.JPG

Re: E50 first start, piston contact?

i promise im not a robot /

alright just wanted to say i appreciate the continued advice and ideas here, awesome to have such moped-minded folks to bounce thoughts off of and learn from. this thread has kind of just turned from the initial rattle problem to my stream of consciousness as i sort this bike out so maybe something thats written here will help others in the future.

ditched my base gasket for one made from a paper bag (good call graham), ultra copper'd it and stuck it on. bottom of the transfers are still maybe 1mm higher than the piston at bdc but its an improvement. gonna see how this works before i resort to cutting metal, though ill probably do that eventually when chasing more speed. put it back together and my squish is around 0.050" neighborhood which is still high but the motor feels much more like i expected when turning it over by hand still not ultra hi hi yet. realized i also had turned my stator to full advance like a lot of people seem to do, but after some research on past comments by roffman ive got it at full retard now (still ~18-21 deg advanced) which i want to check with a timing light when i can get one. shooting for 15-17 deg but ill need to take the flywheel off and dremel the slots if i wanna get there i think, well see how hot it gets like this for now.

Re: E50 first start, piston contact?

you could get mars to countersink your head...personally, when assembling it if i noticed the kit was that far off i woulda sent it back...that's a lot of work you've done...

Re: E50 first start, piston contact?

Matt Mahloch -- MBM Customs /

Sounds like you're getting a handle on it. I don't even run a base gasket on some stuff, just a product call the right stuff.... probably not much different then a paper bag. Then a countersunk head will be a must. You can also take a little off the top of the cases when/if you ever pull them apart. I imagine you'll still be too high on the top. You can always deck the cylinder but that lining likes to chip which is shit. Good deal.

Re: E50 first start, piston contact?

sounds like piston slap to me!

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