Re: new have some questions

@manny,

good job, i did not mention that because i did not know if you had a welder.

Re: new have some questions

manny gouveia /

RABBITHOLE.

So I was determined to try to see the compression above 25 psi and put a drill to it on the stator side didnt happen! but what did happen was I stripped the crank some and the nut

SoI guees I am going to need a new crank.

Dammit after I did that I pulled the head off and the bore and Piston looked great.

amyone know what thread is on this crank? or is it junk now I am thinking I might be able to salvage it with a rethread die.

av7 5V also going to need rings since I have it open..

arggghhh

Re: new have some questions

Yeah trying to start mopeds with a drill is not advised for this reason.

It should be 11x1 mm right hand thread, it's a super odd size.

I don't understand what you are doing but there is probably nothing wrong with the moped. The loose balls are normal, you should slow down before you make a mess out of things.

Re: new have some questions

manny gouveia /

> Graham Motzing Wrote:

> -------------------------------------------------------

> Yeah trying to start mopeds with a drill is not advised for this reason.

>

> It should be 11x1 mm right hand thread, it's a super odd size.

>

> I don't understand what you are doing but there is probably nothing

> wrong with the moped. The loose balls are normal, you should slow down

> before you make a mess out of things.

Yea thanks for that, gotta learn right.. penny wise $ foolish

well the damage is done! need to move on..I am debateing just buy a short block..

I wouldnt mind. some mph, from the little research I have done I can make this a solid 35mph bike.

I also would love to get a bigger piston. " size matters" I see they have bigger heads for the AV7 block..

the way I see it is I am needing a new crank..... again comes back $ wise penny foolish.

I like the idea of originality, But I have seen some complete engines AV10 for 450.oo AV7 on Ebay 659.00

I like the Idea of fixing it and work with what I have

wish I could read french :).

your thought ? (edited)

Re: new have some questions

you should just try to fix it! plopping in a new crank and bearings is one of the next things on my list to do over the winter. I just want to learn how to do it for future builds. And there are plenty of tutorial vids to watch --- - dave fixes his shit --- on you tube. and pop on a treats cdi while your at it!

stripped out threads is very uncool. re threading the crank arms seams sketch too but finding the right size die could be difficult. but if it works then great!

please dont buy one of those complete engine clones on ebay. i just couldnt trust that they are bench tested and work properly under load. youd probably have to take it apart and inspect the cylinder and case anyways -- too much money and headache.

Re: new have some questions

manny gouveia /

thanks for that!

Re: new have some questions

Pushrod Fifty /

At this point, sell it for parts and find a different hobby.

Re: new have some questions

That nut is there only to hold the flywheel on the shaft .

Why not re-thread the shaft end with a size smaller ?

Lap the flywheel to the crank and run it .

Cost of the die and new nut is the extent . So , for under 10 bucks ...

Re: new have some questions

manny gouveia /

am currently looking into that. but if a new crank is in order thats what it will be.

I am curious why only reading 25 psi thats a far cry from 120 that someone suggested I need.

Re: new have some questions

manny gouveia /

> Pushrod Fifty Wrote:

> -------------------------------------------------------

> At this point, sell it for parts and find a different hobby.

thanks lol

Re: new have some questions

> manny gouveia Wrote:

> -------------------------------------------------------

> am currently looking into that. but if a new crank is in order thats

> what it will be.

>

> I am curious why only reading 25 psi thats a far cry from 120 that

> someone suggested I need.

Another fellow on this site was getting low readings , too . He tried a different tester and the readings went into a more acceptable range .

Re: new have some questions

manny gouveia /

I can definiatly try that...the bore and piston or in great shape,,popped off the head decompress valve also in good shape.

Re: new have some questions

There is such a thing as moped finess, post all carnage picts.

Re: new have some questions

> pat splat Wrote:

> -------------------------------------------------------

> There is such a thing as moped finess, post all carnage picts.

Most definitely . ;)

Re: new have some questions

manny gouveia /

> Pushrod Fifty Wrote:

> -------------------------------------------------------

> At this point, sell it for parts and find a different hobby.

lol up yours

if you dont break it you cant fix it

Re: new have some questions

manny gouveia /

still scratching my head.installed new rings and did compression yest it is acually a little less looks to be 27lbs down from thirty prior to the ring replacement..... the rings are installed correctly .. replaced head gasket along with base gasket no sign of decompression valve leaking...I ordered a new comp gauge see where that takes me...

It justs seems to me that 120lbs for a little two stroke seems like a lot.

Re: new have some questions

Are your crank seals shot? Leak down test may be in order.....?

Re: new have some questions

manny gouveia /

I can do that! and will as soon as I my new compression gauge comes in and try that I am not sure why and how crank seals would effect the compression in chamber?I have been doing compression tests with no carb installed and no exhaust

Re: new have some questions

Saints! You guys are SAINTS, I tells ya! Taking all I got not to pop off and crack wise. Can’t help but wish this set of posts was about a Tomos. There, I said it

Re: new have some questions

Dirty30 Dillon /

Judging by the whole arch of this thread, either your tester is incorrect, or you're mucking something up with the assembly/disassembly. 100~ is what I consider a strong running PSI, 30 psi won't even start a moped.

If you are going to keep the bike, rebuild the motor. AV7's are pretty notorious for bad seals. My guess is that you are installing the head while it's hanging from the frame, and something is not sitting right.

Or, your topend is more clapped/worn/out of round than you think.

Re: new have some questions

manny gouveia /

Idont know about head being warped but like I mentioned before I pumped air into it and held the crank and it held the air no leaks,this ws before I replaced the rings..I have another compression tester coming in,.

Could well be I have a faulty gauge, we will see soon.

Re: new have some questions

manny gouveia /

> Stephen Keller Wrote:

> -------------------------------------------------------

> Are your crank seals shot? Leak down test may be in order.....?

Re: new have some questions

manny gouveia /

Did a leak down test.. seems good didn’t vary more than 4 psi.

I found the Moby service manual and on page 5 lists compression for the Moby, it reads between 6.5 thru 9 I am guessing psi.

Can anyone confirm these numbers.

I am at a stand still because of conflicting answers.

Re: new have some questions

> manny gouveia Wrote:

> -------------------------------------------------------

> Did a leak down test.. seems good didn’t vary more than 4 psi.

>

> I found the Moby service manual and on page 5 lists compression for the

> Moby, it reads between 6.5 thru 9 I am guessing psi.

>

> Can anyone confirm these numbers.

>

> I am at a stand still because of conflicting answers.

They are talking BARs , not PSI .

6.5 - 9 bars = 'about' 95 - 130 psi .

Re: new have some questions

Compression testing is pretty much useless on a Moped, it's either good or it ain't and you can feel the difference by hand.

Moped engines will run as low as 80 psi, like a stock batavus, but if the rings leak it will act like an air leak and that will mess it up

Re: new have some questions

> Graham Motzing Wrote:

> -------------------------------------------------------

> Compression testing is pretty much useless on a Moped, it's either good

> or it ain't and you can feel the difference by hand.

>

You should say : can feel the difference by an experienced hand .

Because a noob won't know the difference and is easily fooled .

Re: new have some questions

manny gouveia /

> P D Wrote:

> -------------------------------------------------------

> > Graham Motzing Wrote:

>

> > -------------------------------------------------------

>

> > Compression testing is pretty much useless on a Moped, it's either

> good

>

> > or it ain't and you can feel the difference by hand.

>

> >

>

> You should say : can feel the difference by an experienced hand .

>

> Because a noob won't know the difference and is easily fooled .

Re: new have some questions

Graham’s right for my money. Even the Harbor freight compression tester that everyone uses reads 20-30 psi low in my experience. My theory is that it’s not designed to read such a small volume like a moped combustion chamber/ crank case since (in comparison to car cylinders) it’s only like slightly larger than the volume of the hose on those things. The Fred’s Guide version of a thumb over the plug hole has always done me right.

I guess what I’m saying is that you’re getting too caught up on performing the test and diagnosing, whereas if you rebuilt the bottom end and replaced the rings and top end gaskets, which is kinda a standard move when a moped is new to you, you’d be ripping right now.

Re: new have some questions

> iskra chornia Wrote:

> -------------------------------------------------------

> Graham’s right for my money.

Like I said , that's^ fine for an experienced thumb .

I've always said , it's simply a general gauge as to whether there's enough compression . Exact measurements aren't needed .

These are not high performance racing machines . Close enough is plenty good enough .

Re: new have some questions

I still would have maybe cleaned/gapped the points and tried to run it as is, that bike is so clean, it had not been outdoors, I bet it would have fired up. If not check coil and plug lead and plug. No way that thing had roached rings, unless someone ran it on straight gas and seized it, but then it would not turn over. No spark on a Moby is fairly common, what with the bizarro world wiring. I had one that would not start if the headlight was switched off, not that that is a big deal, IF you sort it out, it should run with the light off, but since I never ride with the light off, I did not worry about it. They are NOT normal. :)

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