Curious about the engine, :question:

[maniac57]

Alright, here's the rod on mine:


Normal 38mm stroke but the case looks thicker around the transfers...

Check out my latest porting thread for more details and pics of engine

 

[mapbike]

Yep thats one of the " half breed " engines.

it has the thick heavier crank with good rod, Fred says those engines have real good primary compression but need some work to get timing corrected just like the GT5 engines.

 

[boxcar]

I have the kit pictured in the first post.
Haven't had it apart other than removing the head to clean things up before run in.
The engine has the larger front mount as mentioned and 35mm intake spacing.
Long curved clutch lever.
3 wire mag.
And the newer CDI.

I have the engine in question in a Centrix cruiser frame.

Am running a Delorto clone carb , a long torque pipe and an allen bolt kit from Sick Bike Parts.
As I am new to the " Motorized bicycle " world , I have no frame of reference to compare it to earlier engines.
I have been a bike builder for 35 or so years though ( just a bit bigger bikes).....
So far my observations are:
The cylinder was spotless when delivered .
1 head gasket.
Came with ( what I believe to be ) the old style NT carb. ( never ran it )

A different style exhaust than I have seen on the exhaust posts here.

After removing the end cap the I discover'd that the cap had a short tube extending into the muffler housing 1.5 -2" and that was it.
All of the other workings of the muffler were welded inside the housing ( I assume to the forward cap ).

Running a 24-1 mix for break in .
With the stock plug.
It runs very smooth .
Almost no perceivable vibration.
Has good torque out of the hole.
Decent top end (34 mph) GPS...
Runs cool ( winter testing )
And is of good quality.
I have order'd a second unit from the same seller .
I will be adding a Fred head, some port work and a different pipe to this one for comparison .
As I now have an old Hawk engine and a 6 year old from an unknown supplier ( Funny how things tend to breed )
to make comparisons against I'll let you know what I find out.

 

[mapbike]

that sounds great boxcar, nice looking bike by the way.

Im starting to think these engines are of good quality, I know Fred has even said that thr cranks are good and generally of good balance and give engine good primary conpression since the counter weights are thicker than what comes in the other pk 80 & GT5 engines.

I guessss at some poi t in the future Im gonna have to give one a shot myself and see how it performs.

thanks for sharing this great info boxcar.

such an excellent thing about this forum, so many good people sharing so main good things.

 

[boxcar]

As promised I will now show at least some of what makes this China girl a bit different.
I just received my second engine kit from

http://www.ebay.com/usr/song-top?_trksid=p2047675.l2559

I have done a quick top end tear down and photographed it for your enjoyment.
I have not cleaned or alterd this engine in any way........
What I found fallows:
Single head gasket......

http://www.use.com/media/2015/0128/4212726/p_004.jpg

 

[boxcar]

More:

Not mutch porting required here.
The gasket and intake match the cylinder exactly.
I may enlarge the inlet a bit though.

 

[boxcar]

More again:

Notice the 2 base gaskets???

As I am no expert with these engines I will take questions and or make mesurements for any one who needs them.
What I do know is strictly from the experience of running the same engine for 100 miles in a cruiser frame.
It's seems to have plenty of torque / is very well balanced / pulls hard up to about 8000 rpm with little effort.
I have been clocked to 34.5 mph ( garmin gps )
44 tooth stock sprocket. 26" wheels.

 

[Davezilla]

That looks very similar to my first kit, Mine was running nice out of the box (only Fred head added before first startup) and I put about an hour and a half run time on it when I noticed my crank had a LOT of side to side play. I took it all the way apart to find a way to remedy this problem but in the process trued the crank, it was pretty bad, but they ture up nicely and easily. ordered new bearings, gaskets, and everything else I needed but wanted to work the case and crank better before reinstalling.
I bought a Dax bottom end to get the bike back on the road and this bottom end was way smoother running so I kept it in the bike. I did a LOT of porting and other fixes while waiting on the new bottom end, but also finished the other bottom end so it's ready to reassemble but I'm going to weld the crank and make a set of shims to get rid of that free play it has first.

For the good... the jug was very nice and had large ports to begin with, they're larger now but were nice stock.
The shorty intake, this one is one of the few that actually matches up to the intake port, most just have a small round hole at teh flange and not a lot of room to match port. only thing I did here was bore it out to 16mm because the stock 13mm hole on the intake manifold is restrictive and prevents higher rpm.
The piston and rings... nothing special here but they're nice and went back in the engine that I'm currently running.

The bad...
Very cheap crank and clutch bearings... I'd recommend changing these before even running, one crank bearing was already noisy and rough after only 90 minutes of run time, and one of the clutch bearings was in even worse condition.
The crank was just plain sloppy... over .020" runout when first measured. I corrected it to nder .002" runout and the crank wheels had a ton of side to side wobble from being improperly assembled... I'm surprised it lasted 90 minutes... most likely what toasted the bearing and casused the side play.

I definitely make sure I know something about the engine and the seller before purchasing after seeing how sloppy this one was assembled, it had some good parts, but I'm thinking the lac of quality control on the assembly line and the cheap bearings are what would have killed this one on short order if I didn't give it that look over when I did.

 

[mapbike]

Keep the pix coming boxcar, I'd like to see one down in the jug when piston is at bdc and I'd like to see a pic inside exhaust port when piston is at bdc.

I've thought about getting one of those engines but would like to see more of it first.

I'm also curious about whether they use the pk-80 piston or if they use the GT5 piston.

 

[boxcar]

Good to know.
I'll be cracking the cases tomorrow. Will check the crank and post what I find.
I will say this.
The first engine is as smooth as silk.
Shows no sign of crank or clutch bearing failure.
You may of just gotten a bad motor.... Or I may have gotten lucky....
I'll take pics of the ports tomorrow as well.
Thanks for the responses.

 

[mapbike]

Good to know.
I'll be cracking the cases tomorrow. Will check the crank and post what I find.
I will say this.
The first engine is as smooth as silk.
Shows no sign of crank or clutch bearing failure.
You may of just gotten a bad motor.... Or I may have gotten lucky....
I'll take pics of the ports tomorrow as well.
Thanks for the responses.

Did you get the first engine from song-top?

I've bought a couple things from that seller, quick shipper and excellent communication.

 

[Davezilla]

Could be I got a bad engine, like I said I would have never noticed a problem but I wanted to check the magneto because the engine was developing a sputter and that's when I noticed the crank could slide side to side about an eighth of an inch.... the sputter turned out to be debris in the carb... I could have got a bad speed carb too but the debbris was the rubber shedding off the built in fuel valve.

The crank it's self I'm sure wasn't assembled right or carefully enough, it was really bad.
the top end tho was really nice with big intake and exhaust ports and nice wide flat top transfers, and the piston assembly with a wider roller bearing was all installed on a Dax lower to make a very smooth running engine... not even a slight buzz on the hands at 9500+ rpm.

Hopefully mine was just bad and not all of them are that bad, there are several factories in China that build and assemble these so it may just look a lot like my first engine.
I'm Very happy with the top end on the Dax bottom end tho.

 

[Davezilla]

I forgot the sellers name but I know it wasn't song top I got mine from, I can look it up next time I'm on a computer tho. I also remember this seller was about $10 less than the other sellers so maybe he got a deal on the quality rejects and sold the ones that looked ok or were completely assembled... who knows but I'll stick to reputable sellers that I know something about after that one.

 

[boxcar]

Yes . Both engines from Song Top.
I had the mag cover off the other day to install a generator from Wonderful Creations.
No sign of crank movement . I do like the gennnnnny........

 

[cannonball2]

Guys, that's not a half breed(see link). It(the half breed) has a ZAE50 rod. If I am seeing it right its an 80. That's the rod Fred says in his crank vid he has never seen. Its grouped with the GT5 engine with the FM80 rod. It is 38mm but has a much longer rod(if he is right and they are the same). This crank runs the high pin piston. Look for fine cyl stud threads. http://motorbicycling.com/showpost.php?p=592321&postcount=41

Heres some are some comparison pics of the Dax, ZAE50, and the FM80/GT5. I have been wrestling with this crank thing down in my scratch build thread. pic1 ZAE50/FM80 pic2 Dax/FM80 pic3 ZAE50/Dax the dax appears a 38mm instead of the advertised 40.

 

[mapbike]

Guys, that's not a half breed(see link). It has a ZAE50 rod. If I am seeing it right its an 80. That's the rod Fred says in his crank vid he has never seen. Its grouped with the GT5 engine with the FM80 rod. It is 38mm but has a much longer rod(if he is right and they are the same). This crank runs the high pin piston. Look for fine cyl stud threads. http://motorbicycling.com/showpost.php?p=592321&postcount=41

Heres some are some comparison pics of the Dax, ZAE50, and the FM80/GT5. I have been wrestling with this crank thing down in my scratch build thread. pic1 ZAE50/FM80 pic2 Dax/FM80 pic3 ZAE50/Dax the dax appears a 38mm instead of the advertised 40.

I have an engine with the ZAE50 rod, the "Half Breed" engine, piston doesn't completely clear exhaust port at BDC and piston stops shy of being even with cylinder deck at TDC by about 0.0625" just like Fred had said it would be.

My H-B engine has good low down power but has a lower top end than the Older GenIV 40mm stroke dax engine with the same mods to the cylinders ports, the H-B needs some other mods to get it to perform as good as the 40mm stroke engines.

The newer Dax engines are 38mm stroke GT5 type engines.

After going back and looking at the pix CB2, I can see what you're saying, looks like the 3rd pic shows the ZAE50 rod to be the same exact length as the GT5 type rod thats in the newer Dax 38mm stroke engines....! OK now I think I'm officially confused since the Newer Dax engine uses the high pin GT5 piston.

YesImLDS, has one of the newer dax engines and it looks to be simply a GT5 engine, 38mm stroke and high pin piston.

Freds Video explains different engine geometries and rods that depict which engine we have. (Or does it?)

http://youtu.be/rzLWYSlpFEg

 

[cannonball2]

Map, maybe Im missing something? The rod in the link is a ZAF80, the missing rod in the vid right? Its a 38mm long rod(114mm) to be used with the high pin piston. The FM80 a 38mm stroke crank with a long rod. Both rod/crank combos make a GT5 and I betting the piston comes to the top of the jug.
The ZAE50 is a 38mm short rod(110mm) and will come up about .062 low in the jug, hence the 1/2 breed. I have a Flying Horse that has the 40mm crank with the ZL rod. That's a standard 40mm engine. Daxes used to be that way, but the Dax I have now is 38mm, making another 1/2 breed in a standard jug. So there have to be different jugs out there. Or the long rod 38mm GT5 will pop out of the jug.

Right?

 

[mapbike]

Map, maybe Im missing something? The rod in the link is a ZAF80, the missing rod in the vid right? Its a 38mm long rod(114mm) to be used with the high pin piston. The FM80 a 38mm stroke crank with a long rod. Both rod/crank combos make a GT5 and I betting the piston comes to the top of the jug.
The ZAE50 is a 38mm short rod(110mm) and will come up about .062 low in the jug, hence the 1/2 breed. I have a Flying Horse that has the 40mm crank with the ZL rod. That's a standard 40mm engine. Daxes used to be that way, but the Dax I have now is 38mm, making another 1/2 breed in a standard jug. So there have to be different jugs out there. Or the long rod 38mm GT5 will pop out of the jug.

Right?

Yeah I think your right, thats why this just got a bit confusing...LOL!

as you can see I went back and edited my other post after I read through your post again, initially I didn't understand what you had said so I had to go back and reread my post to see that I was off base with what you were trying to explain.

Yeah if the low pin piston is used on the long rod the piston will be way out of the hole.

What has me bumfuzzeled is that YesImLDS has the newer dax engine also and his has the high pin GT5 piston which would typically mean the engine is a GT5 standard type B engine, but if your engine has the 38mm stroke crank, the short rod plus the high pin piston, no way the jug can be the same and I would think that the piston skirt would hit the counter weights on the crank before piston would reach BDC.

Am I off base and missing something here...?

the 3rd pic you have listed shows the newer dax to have the same rod and stroke as the Half Breed ZAE50 rod engine.

Does your newer dax engine have the GT5 type B piston?

 

[cannonball2]

I only have the Dax crank. I bought it as a replacement for my FH engine thinking it was a 40mm stroke as advertised. He lists a 115 rod length in the add. Cant be with a 40mm stroke unless he has the jug to match. I suspect he is using the 38mm/110 rod/low pin type piston, but have no hands on to know. This engine I have in pieces must be a GT5 as the head studs are fine thread. If the piston on the long rod tops flush with the cylinder, then there is a GT5 jug. Its the only way it can work. The half breed engine in the 40mm jug and comes up 2mm short. Both SHOULD come up way short in the GT5 jug.

This is confusing!

 

[cannonball2]

No wait it adds up! 38mm stoke+4mm(114 rod) rod length+ high pin piston probably equals the 40mm jug. Running a 38mm/110rod crank with the low pin piston was an easy way to use a 38mm crank in a standard 40mm jug, it works buts not designed to. That's why its a half breed better read, bastard engine. A bad marriage of the combo pieces. Must have a bunch of 38mm/110 cranks to get rid of.

Moral of the story may be stay away from 38mm/110rod cranks looks like the jugs are designed for 40mm. I guess the reasoning for wanting the ZAE50 rod crank was the supposed balance. Means a lot of jug/port work, don't know if its worth it.