Curious about the engine, :question:

[mapbike]

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!

Yeah I dont know what to think about all this.....LOL

If the new crank you have from dax has the same rod as the crank you have that has the ZAE50 rod, then the newer dax crank will have to be used with a pk-80 type A jug and piston and then what you will have is the exact same geometry as the "half breed" engine and that engine will benefit from the same corrections as the ""original"" "Half Breed ZAE50 rod engine"

YesImLDS has one of the complete newer dax engines, and after pulling the jug he found that it has the rod marked ZAF80 and has the high pin pistn (Type B)

Does the new dax crank have any markings on the Rod?

 

[mapbike]

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.

So maybe a {mamzer (mam‑zare') } a mongrel....!

Maybe it could be called a "Heathen"

you may have it narrowed down here now.

 

[cannonball2]

The Dax rod has no markings. The FM80 is of course a GT5 crank and the high pin piston makes it a GT5 engine(type anyway). Bet the threads are fine. That combo should time pretty well at least better than the half breed.

Did you see my edited post where I theorized that the GT5 adds up to run the 40mm jug, probably with minor timing issues.

So Im guessing all the jugs are for 40mm stroke, unless of course there are specialized jugs for specific manufactures engines.
Cant wait to get the bearing so I can assemble this engine and see the results on timing/travel.
The 2mm travel means a lot in timing.

 

[mapbike]

The Dax rod has no markings. The FM80 is of course a GT5 crank and the high pin piston makes it a GT5 engine(type anyway). Bet the threads are fine. That combo should time pretty well at least better than the half breed.

Did you see my edited post where I theorized that the GT5 adds up to run the 40mm jug, probably with minor timing issues.

Can't remember if I read that post or not CB2, I do know that I talked to Fred through email a while back and he told me that the PK-80 type jug works out good on the GT5 engines as far as timing is concerned, it just needs about .100" shaved off the deck height to get compression and squish where it needs to be.

I have a GT5 engine in the works soon, and I'm gonna do a comparison of the port timing between the GT5 jug and the PK-80 jug on the GT5 lower and see if I can tell any difference other than the deck height.

 

[mapbike]

Another thing I noticed about the engine I have that has the ZAE50 rod is that the threads in the case are fine threads and the top of the studs are coarse threads like the typical PK-80 engines, I also have an old BGF ngine that has studs that are this way, I biought that BGF engine back in 2010, it has the low pin piston but I have no idea what crank it has, been to long since I've seen it.

Another thought that just came to mind is this, if you look at the lower rod journal pin on both of the cranks, does the bottom edge of the pin come closer to cranks main shaft on one than the other?

Here is a pic I just took of the extra ZAE50 crank I have.

 

[mapbike]

Here is a pic of another crank that came out of an engine I got from LEB/BGF about three years ago, I never noticed before but it has ZAE50 on the rod also, but this rod is thicker and made a little different than the ZAE 50 rods that are being put in these latest engines, looks like this would be another type that Fred hasn't seen yet or at least didn't mention in his video.

The counter weights/flywheel weights aren't thick like the newer version either, this crank has the same width weights as the original dax GenIV FM80 engine, the measurement is the same bewteen these two ZAE 50 marked rods when I measure distance between main journal and rod journal, this older ZAE 50 rod and crank looks a little better in spme ways and a little rougher in others, this older engine also came with PK-80 Type a jug and piston, so it seems that this "Half Breed engine is actually nothing new at all but has been around for a long while, at leats since 2010 or so.

fist tow pics are of marking on older ZAE50 rod, second pic is a comparison of weight widths between the two ZAE50 rods which are the same stroke set ups and then we have the original dax GenIV crank and rod in the third pic, by far the best looking of all the cranks and best overall looking rod as well, the rod bearing is tight and smooth and the machining is very nice a nd clean.

the distance bewteen the main crank shaft and rod journal pin is 4.20mm vs the 3.75mm measurement i got on the two ZAE50 marked cranks, I'm guessing the 3.75mm measurement would be true also for the GT5 crank.

the original dax being a true 40mm stroke crank, and a much better looking piece than any of the others I have seen hands down.

I sure wish I had known dax was gonna crap can the good cranks and lowers, if I had known I'd sure have bought up a few for future builds...

Keep in mind here that my measurements aren't completely perfect since I'm just having to eye ball a little with the calipers, but it's darn close.

 

[frank66]

you guys have me confused. but i have a zaf50 and a zaf80 here and i want to get it right aswell. how can i help?

 

[mapbike]

you guys have me confused. but i have a zaf50 and a zaf80 here and i want to get it right aswell. how can i help?

So I'm guessing the zaf80 rod is actually for a 40mm stroke engine like the GT5A?

I think the main thing CB2 is looking at here is his trying to figure out if the newer dax engines have anything different about them than the others.

I know at least one member here has one of the newer dax engines and it has the 38mm stroke crank marked zaf50 and it has the high pin piston in it which tells me its a simple Type B GT5 configuration.

The new crank CB2 got from sax looks to me like one that would be used to make up a Half Breed type engine by using a Type A jug and low pin piston.

 

[cannonball2]

So to formally pose the question: Is there a 40mm timed jug and a 38mm timed jug? Logic says there should be. Why make two different strokes and run them in one jug? There must be a 38mm specific jug. I think we have the crank variations more or less understood. Now we need to figure the jug situation out. Some one went to the trouble to make the 38mm crank, there must be a jug, or it just doesn't make sense, unless somebody set the CNC up wrong and didn't discover it until they had 10,000 sets.

 

[frank66]

both my zaf50 and zaf80 are gt5a but i disagree see below.

. they both are 38mm stroke i believe. 40mm inlets on both. large transfer tunnel.

i have seen two blocks with large or small transfers passages aswell.

i have never seen a pk80.

there is no specific engines just choices. 3-4 cyiinders. 3 rods. 3 blocks. 4 cranks...... 4 pistons. 5 heads etc etc.... when buying the grubee's anyway.
the pk80 i dunno.....I dont know how may ways you can build the 40mm stroker....
--WARNING I COULD BE WRONG--

 

[cannonball2]

This is even more confusing maybe. If the ZAF80 uses the short piston then it must have a taller rod. Im thinking the 80 may designate the 114mm rod. If the ZAF50 is 110 on the rod and uses the tall piston then its the half breed will be .062 in the hole. A ZAF50 with a short piston would be so far in the hole it might not run.

I think.

 

[frank66]

i could start a thread documenting measurements but its impossible to locate cylinder a/b or c.

im game for that anyway..... interested anyone?

 

[mapbike]

I have several jugs "specifically" for the 40mm stroke engine and I have one jug that is specifically for a GT5 engine I will do some examining and see if I can identify a difference other than deck height.

I know there has to be some very thorough posts on the subject here on the forum.

I've never until lately mess with the GT5 engines, I remember people talking about the 38mm & 40mm stroke cranks on here over the last few years, I do know that the current buzz about the " Half Breed " engine isnt new, it turns out that at least one of my older engines has the 38mm stroke crank but uses the PK 80 (Power King) piston and jug type.

It will be a couple days until I have time to dig my parts out but ill do comparisons with each jug and both a 40mm stroke pk 80 style lower and a GT5 lower.

If someone has time to do this before I do be sure and post pics of all of it.

 

[frank66]

im not sure about my findings. i heard the zaf50-80 were different lengths so i assume the piston makes up for it. im really not sure im correct past being able to read the rod stamps

 

[frank66]

ok i just slid my jug on and its a gt5a with a zaf80. i thought it was a zaf50 so i was wrong.

the piston sits a little low on the deck!!!

 

[Greg58]

I was confused about which piston works with which crank and with which cylinder does best for port timing etc.... Long before I read this thread intirely. Now I'll have to follow just to see what y'all figure out!

 

[mapbike]

I was confused about which piston works with which crank and with which cylinder does best for port timing etc.... Long before I read this thread intirely. Now I'll have to follow just to see what y'all figure out!

I do know that the ZAE50 stamped rod engine has to go with a pk80 type jug and piston thats typically used on a 40mm stroke engine, I have two of these engines and both need that set up, the main issue with the HB engines is that the pk80 type jug is a 1/16"/ .062" to tall and at BDC the piston doesn't fully open the exhaust port, also think the HB type engine just like the GT5 can benefit from some slight piston ramping at the transfers as well as maybe just a little on the exhaust side of piston, I think possibly that these engines will perform better in the higher rpmsif two base gaskets are used and for sure the deck height needs to be brought down a good bit, maybe as much as .070 ot so if two base gaskets are used.

im gonna experiment a little with mine just to see what if any gains will be realized when I raise the ports, shave the deck and add some ramping to piston but ramping will be just a small amount so hopefully I dont kill the bottom end grunt to much.

 

[mapbike]

ok i just slid my jug on and its a gt5a with a zaf80. i thought it was a zaf50 so i was wrong.

the piston sits very low on the deck!!! im shocked! it comes down way to far aswell. this is not good.... i need a taller piston. im shocked silly.

seems the problem you describe here is something all GT5 and Half Breed engines have, no way theze engines can reach full potential unless deck height is brought down, the extra low compression may be one of the reasons some people get such long life from these type engines.

the bearing aren't stressed nearly as much, personally I like the power and better cruise speeds even if it does shorten the life a bit.

 

[Greg58]

Hey Shan if you raise the jug to improve exhaust timing are you notching the skirt on the intake side to compensate ?

 

[Davezilla]

Now to add even more confusion, I pulled the jug off my other engine to see what rod it has and it's blank on one side and on the other side there's "CY" cast onto it... Anyone know anything about that one...