Yamaha U7E

mouka zwina /

Howdy all?

I have found a nice 1972 Yamaha step through scooter. It is not a moped per se. However I know I will find some help here.

The electric start is not working and this bike is missing the kickstarter. I was able to push start it but it runs rough. I took her home cleaned up the carb and now it runs fine and idle fine. However I am annoyed at the push start business and decided to find a kickstart lever. I scoured the internet and found the assembly selling for over $120 including shipping. I paid only $400 for this bike and I am not willing to pay that much for a stupid lever.

I was wondering if someone has something like that and are reasonable enough in their asking price.

Peace!

Re: Yamaha U7E

I am obliged to post NOT A MOPED before being helpful...

Shaft size is same on many small cc Yammy bikes, check with a dirty bike guy in your neighbourhood for something like a MX80 kicker or something and bend to fit...

Re: Yamaha U7E

mouka zwina /

Thanks. That's what I was thinking but was not sure about the shaft size.

I meant scooter shaft and nothing else you twisted minds!

Re: Yamaha U7E

you could use a pedal arm and pedal or use a vice grip wrench.

Re: Yamaha U7E

Re: Yamaha U7E

Rob @t ATTN! Burrito /

i have one with the same issue. shaft and kicker arm stripped. was thinking spot weld since they're both jacked anyways. a running u7 for 400$ is a pretty good deal btw

Re: Yamaha U7E

You should be able to use any small cc Yamaha jti 60 gt80 ect... just look on ebay....

Re: Yamaha U7E

yea just measure it. there aren't that many kickstart shaft variations. a lot are common sizes even across brands.

also I love those bikes. it's like a 2 stroke and a cub. luvvv

Re: Yamaha U7E

Re: Yamaha U7E

If the shaft is stripped then position the kicker how you like then drill a hole to go through the kicker and shaft and throw a pin in it. Tack welding the kicker is not always a goodly idea because if you have to crack the casings for anything you will be screwed, also welding can draw the temper from the shaft making it softer.

Re: Yamaha U7E

mouka zwina /

I have not had any success in getting it to run. I ordered a new carb and Kickstart et from ebay. I should receive the carb this week. The Kickstart is a different story as it is coming from Thailand.

Anybody knows where I can find the service manual for this scootet?

Re: Yamaha U7E

ahh yeah auto trans, you cant push start! bummer.

you can probably use 'freds guide' as a primer, since what you have is basically a moped.

Re: Yamaha U7E

mouka zwina /

I have made a lot of progress since I got this cooter. However I am completely puzzled by the fact that this scooter does not run yet.

I have checked the spark and it has a very decent fat spark. I did not check compression yet, however I have just used my hands to have a feel for the compression and I can say for sure that this scooter has good compression. I will have an actual figure for the compression tomorrow after I come back from work.

I tried injecting starter fluid directly but I can't get the bike to start.

I hooked the battery to a running bike and tried for several minutes to start this scooter but nothing has worked.

I have cleaned the carburetor and I know that all the jets are clear.

I had it starting for a very brief moment a few days ago when using starting fluid but it did not last for long.

I now have the electric start fully operational but the damn bike does not want to run.

Any ideas would be greatly appreciated.

Thanks!

Re: Yamaha U7E

Overpriced Parts /

Spark not in time

Air leaks/bad engine seals

Broken-stuck rings/bad compression

Re: Yamaha U7E

mouka zwina /

I am suspecting bad timing. How do i fix the timing of my engine?

Re: Yamaha U7E

should be points. just look at when the points just barely begin to open compared to the position of the piston. (take plug out, put some feeler down in, find TDC) should be just opening somewhere around 15-20 degrees or ~2mm BTDC. I'm just spitting baseline numbers, actual timing for that bike will be different but around there. if you're around there it should be close enough. Also can check point gap when they're most open but that'll be wholly bike specific.

the points just barely begin to open technique is easiest for quick checks.

Re: Yamaha U7E

mouka zwina /

Do the engines of these 2 stroke scooters have a reed valve? I am not 100% sure that all 2 stroke engines use a reed valve. I could be wrong since I have not worked on a 2 stroke engine in a very long time.

The reason I am asking this question is that this could be one cause for the engine not running.

Anybody has some input on this valve issue?

Thnks

Re: Yamaha U7E

mouka zwina /

Born to be WillD Wrote:

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> should be points. just look at when the points

> just barely begin to open compared to the position

> of the piston. (take plug out, put some feeler

> down in, find TDC) should be just opening

> somewhere around 15-20 degrees or ~2mm BTDC. I'm

> just spitting baseline numbers, actual timing for

> that bike will be different but around there. if

> you're around there it should be close enough.

> Also can check point gap when they're most open

> but that'll be wholly bike specific.

>

> the points just barely begin to open technique is

> easiest for quick checks.

What are these points you are talking about? I have never really worked on a problem scooter before and I am completely at a loss to know what you meant by points.

Can you please talk in layman terms so i can follow you and maybe find something that can help me fix this scooter?

Thanks!

Re: Yamaha U7E

ignition contact breaker points.

The U7's are p-sweet. Brush up on some basics, and you'll have a grand old time. The suggestion to check out freds guide is a good one.

Re: Yamaha U7E

mouka zwina /

Deadped Ryan Wrote:

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> ignition contact breaker points.

>

> The U7's are p-sweet. Brush up on some basics, and

> you'll have a grand old time. The suggestion to

> check out freds guide is a good one.

What do you mean by p-sweet?

By the way, I have read the entire Fred's guide and I think I have a pretty good on what to do next.

Re: Yamaha U7E

mouka zwina /

I went ahead and purchased a compression test kit and the verdict is in: I am reading compressions of just a tad over 40 psi. I know that good compression should be at least 100 psi for it to run. The proper value I think should be 150 psi or above.

What do you think is the probable reason for such low readings? I am suspecting piston rings but I am not 100% sure.

I also checked the timing and found the points would open at, or very near, top dead center. However I also noticed that they stayed open even after that and close after about half a revolution. Is this normal for this type of scooter?

As usual: Thanks a million for your invaluable input.(edited)

Re: Yamaha U7E

If you really wanna be cheap about it, best bet would be dump some penetrating oil or PB blaster down in the cylinder. Hopefully the rings are just varnished over. No reason they should shatter.

More likely though, is someone ran it out of oil or the injector failed, and smeared the piston on the wall. Pretty sure those things are injected.

TL;DR; prolly time to pull the cylinder and head.

Re: Yamaha U7E

mouka zwina /

I ended up throwing away those rings. I don't know about the scooter running without oil. I am guessing it could have happened.

Anyway I have decided to buy a new set of rings and see if this solves my problem. I have a feeling this is the case.

Re: Yamaha U7E

So you pulled the cylinder then? What does everything look like?

Re: Yamaha U7E

mouka zwina /

i honestly do not know for sure. Everything seems normal. Even the piston rings looked fine to me. I ended up cracking both rings and ordering new ones.

I will post pictures of what everything looks like and the experts here can tell for sure.

One last thing; Was I right in assuming the piston rings were worn out and would leak and not allow a good compression inside the cylinder?

Re: Yamaha U7E

Well, that depends on what the cylinder and piston look like.... if you aren't sure what to look for, post some pictures.

Were the rings stuck to the piston? You might save at least one of the ring fragments. Broken/old rings are one of the best things to clean out piston ring lands.

Re: Yamaha U7E

mouka zwina /

Here are some pictures of the cylinder.

I will post a couple more in another post.

IMG_20161026_154400_BURST008.jpg
IMG_20161026_154406.jpg
IMG_20161026_154417.jpg

Re: Yamaha U7E

mouka zwina /

Here are more pictures of the inside of the cylinder.

IMG_20161026_154428.jpg
IMG_20161026_154440.jpg
IMG_20161026_154445.jpg

Re: Yamaha U7E

mouka zwina Wrote:

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> I meant scooter shaft and nothing else you twisted

> minds!

Actually it's a motorcycle :P

Re: Yamaha U7E

Lol. There was definitely some blow by on those rings. Probably a good assumption that they needed to be replaced.

The cylinder looks a little glazed... Maybe find someone with a ball hone to hone it for ya before you install new rings. I don't *see* any scoring. Prolly try and get all the carbon of the piston with a scotch brite pad or emory paper, and clean the ring lands with the old/broken rings. Should be fine!

Prolly lap/dress the head and cylinder too with emory paper/glass/granite/whatever.

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