Is this Right?

[Greg]

Hi:
I have 2 two strokes, but with the price of gas this year, I have decided to buy a fixer upper to sell later.
I bought a non running 4 stroke.
I think I have a problem with timing.
Maybe I have assumed something incorrectly, from watching and reading the valve adjustment information.
I believe the "T" mark on the flywheel when lined up with the mark on the case should be "Top dead center".
(Forgive me if this doesn't work right as I haven't posted pictures in a long time)
Here is the "T" mark lined up.


Here is the position of my piston when lined up at the "T" mark. Is this right?

[90GTVert]

T is supposed to be the top dead center mark. I thought the one on my SunL was bad at 31 degrees off of actual TDC. That's wayyy worse. The issue with mine was an improperly machined flywheel. Replaced that and all was well. I dunno how yours would ever have ran like that. Might wanna start by removing the flywheel and see if it's got the key installed. Without the key, you can clock the flywheel however you'd like.

[Greg]

Thank you!!!
This has a weird back-story from the last owner.
It went something like: it ran but ran slow (I'm thinking valve lash adjustment needed), so he brought it to the shop.
He got mad at the shop trying to jack the bill and took the scooter home not running.
When I first looked at it, the cam was aligned to the "T" mark, but I felt the piston hitting the exh valve on rotation.
I think the scooter shop noticed the "bad timing' and tried to re-time it before adjusting the valves causing the scoot to no longer run.

In removing the head I noticed I only had one dowel pin on the camshaft housing assy. From the base up, how many dowel pins should I have? I need to order some.

[Greg]

Oh, and by the way..
I don't know if this is a coincidence, but this is a SunL too. LOL

[90GTVert]

Hopefully someone else can tell you for sure on the dowels, it's been a bit since I played with a 4T. I thought you could look and tell cause the holes were larger where there should be dowels. I might be wrong.

Mar 12, 2012 8:47:44 GMT -5 Greg said:

Oh, and by the way..
I don't know if this is a coincidence, but this is a SunL too. LOL

I'm so sorry. :laugh: Actually, it ran well after the timing was right. Definitely not the best scoot I've seen, but it worked and I did start to enjoy riding it for a while.

[Greg]

No need to be sorry. LoL
This is not a keeper like my 70cc 2T's.
This is a learning experience and a scoot rescue.
Fixer up, getter running, getter outta here.

Got the flywheel off. Sheered Woodruff key. There is a wear line in the flywheel about 90 degrees out from the slot. Looks like I am to the root of the problem.

[Deleted]

Mar 12, 2012 8:46:45 GMT -5 Greg said:

From the base up, how many dowel pins should I have? I need to order some.

6

[Greg]

Thank you.
2 at cylinder / base
2 at head / cylinder
2 at cam shaft holder / head
Am I right about that?

[Deleted]

Mar 12, 2012 18:42:37 GMT -5 Greg said:

Thank you.
2 at cylinder / base
2 at head / cylinder
2 at cam shaft holder / head
Am I right about that?

yes

[Greg]

I replaced the Woodruff key and got the timing right. When taking off the flywheel, I flubbed the stator windings, so I ordered and replaced the stator.
The scooter now runs and runs pretty good.
It does have a very weird cold starting problem though. It is near impossible to start cold with electric start.
It cranks and cranks but does not start.
Battery is pretty healthy and goes to about 10.7 volts when the starter is engaged.
When the scoot is warm, the electric start will start the scooter no problem.
When cold, the scooter will start with 5 kicks or less so I don't think it is valves or carb, but something electric/electronic.

I tested for spark by removing the plug from the cylinder and it looked good.
Next I am going to test for spark with a plug in the cylinder and another plug hooked up outside.

I think I am losing spark when cold and with good compression.
As of right now I'm leaning toward a weird CDI problem.

[Deleted]

does it turn over slow when cold?

[Fox]

Have you cleaned the carb lately?

Mixture screw adjusted properly?

Have you double checked the valve clearances? .003in. for both is what I use.

[Greg]

Turns over pretty fast when cold, just doesn't start.
It WILL start cold with five kicks. then electric start when warm.
It feels electircal. I tried moving the ground.
Valve lash checked and checked again after I read that that could cause hard starts, but again, starts easily cold by kicking.
I did clean the carb. The air speed mixture may still be off as out weather is fluctuating from 45 to 75 in the last week.
I think the auto enrichener is working because after 5 minutes the idle goes down.
It seems like something does not like the amount of power the starter draws.
Ah, Problem solved!
I tried a CDI (that I forgot I had) from a parts bike. Scoot started right up cold. Idle and air are still a little off but it is getting there.
For some reason, the CDI did not like the lower voltage from using the starter. My guess is it was not a strong enough spark when using the starter.
Thanks everyone for the suggestions.

[Fox]

So it was the CDI. I should have thought of that cause I had a 50cc that did the same thing a while ago and the CDI was the problem. I have a box with about ten CDI's in it some new and some used. It's funny cause with the original one it didn't want to start with the electric starter hot or cold. I tried several of them and it would start up and idle but crap out with throttle then the fourth or fifth one I tried worked. Not sure if I have a bunch of bad ones or if different scooters require a different timing curve?

Anyway, glad you fixed the issue. It's far more fun to ride them than to fix 'em IMO.

[Greg]

My next project is to fix up and sell the parts bike.
Now, I'll need to order a new CDI, and after what you said.... I'm scared! LOL