Timing Mark question & Type "B" engine question

[kittletstv]

A couple new questions in my fact finding expedition for my 2007 SunL 150.

Question (1) Recently when I reset the valve clearance on my GY6 150 I saw several different marks on the flywheel, a "T", an "F" - (to the right, next to the "T"), 2 verticle lines (1 on the left side of the "T" & 1 on the right side of the "F", and a long rectangle with an elongated one sided arrow within the rectangle. I assume that the "T" signifies "Top Dead Center", and the elongated arrow shows "Direction of Rotation". But I don't know what the "F" signifies, or the 2 verticle lines - (1 each on either side of the "T" & the "F"). Can someone help correct me and / or enlighten me on these different marks?

Question (2) I recently found out that I have a Type "B" GY6 150 engine in my buggy when I went to replace the valve cover gasket. Mine is approx. 1/4inch wide, smooth on the valve cover side / with a 3 rib design on the sealing surface towards the head, not the standard single "oring" style seal. I was told by a potential source for a replacement seal that the "B" motor is actually a stronger version of the GY6 150 than the Type "A" having a 1 hp increase over the "A" and that's why it is used frequently in buggies and scooter trickes. But then I was reading online somewhere later that the type "A" engine is the stronger version, not the "B". Does anybody know for sure which is which, and how common are both versions? Then to make it even harder, another site I was looking at after that claimed that there are actually 4 different versions of the GY6 150's -(not different manufacturers, but 4 actual different models). Any ideas? Thanks

[ckau]

As best as we can figure, those marks on the flywheel are not a actual TDC but rather indicate the timing sequence from the CDI. Actual piston TDC is usually a few degrees after the T mark. Most will find Actual TDC by manually turning the motor over with a straw in the spark plug hole or while the head is removed,(most accurate way). Then mark the flywheel for future reference. With a timing light the timing advance seems to sorta match! At idle the case indicator/mark is close to the T and as rpms increase the advance moves the F towards the case indicator. So it seemed to show the timing advance sequence. We referred the T as the trigger point and the F as final or full advance.
From what we have seen , the A engine (smaller cylinder bolt spacing, 4 bolt valve cover)goes up to 150cc. normally found in scooters. The B version was a more commercial version (larger bolt spacing , 2 bolt valve cover, internal reverse, oil cooler up to 230 cc). These were destined for use in small commercial stuff. Like those 3 wheel enclosed cab delivery things you see on Asian streets.
By western thinking, most consider a commercial motor to be stronger and with more HP due to larger displacements but who knows. Personally, I've never seen a definitive comparison. By the way the Chinese mix and match stuff it would"t surprise me to see more than 4 versions running around somewhere.
I had considered using one of the "b" types. The oil cooler provisions, internal reverse and the large displacement were appealing. After further resourcing it appeared there were too many parts particular to that version only and were few and far between so I nixed the idea.

[2SlickNick]

http://www.amsportworks.com/pdfs/LUT...al-14589R4.pdf
If you look on page 27 of the manual for my machine it tells you how to find TDC.

[2SlickNick]

It seemed like every other turn on my fly wheel would hit top dead center( using cam as reference too)

[kittletstv]

Ckau - Were the "B" models the only ones with the 2 bolt valve covers because mine only has 2 bolts, but it uses the extrenal reverse box?

2SlickNick - I checked out & used your manuals info too.

Thanks for the info guys.

[BuggyMaster]

You'll usually have either a 2 bolt valve cover or a 4 bolt. 4 bolt is the most common and may even be considered "modern". Contact Tom @ SYCPowersports. He has great knowledge of the 2 bolt style machines as well as a wealth of other knowledge.

[kittletstv]

Thanks BuggyMaster for your imput. I will contact Tom to tap his brain on my buugy set up. Is the Howitt GY6 150 that much better than the others in your opinion, and do they have Howitt stamped on them? My engine has this stamped on it below the air inlet for the CVT cover, 1S7QMJ on the top of the ID tab, then *070700085* below that on the ID tab. Is there a way to break down these numbers to tell who the manufacturer is , etc?