40mm intake jugs.. Are port timings the same as the 32mm?

Davezilla

Davezilla

New Member
I was just doing a little ebay shopping and saw some cylinder jugs for sael so I clicked the link and noticed right away in the pic that the intake was considerably wider, read the description and saw that it was BikeBerry's ebay listing and they did specify that these jugs do have the 40mm intake bolt spacing. They sell them on ebay and on their site for $27.95 so I've been thinking about getting one for my next engine build. If I do decide to grab a few of these, they'll get more porting before they hit the street but it's nice to know how they're setup before any cutting begins.
 
its allmost the same.

try exhaust port at 24 -25mm down from top of jug and 24mm wide.

transfers at 33-32 mm down from top of jug and 24mm wide.

this is 9000 rpm peak power.
 
The 40mm inlet jugs I get have wider transfers as well as inlet port, and have better port timing too, In my opinion anyway.
But I have seen a few different narrow inlet jugs, so can't say all the 40mm jugs are the same either.
The 40mm jug, has a slanted roof to the transfers, and I like to lift this to a flatter angle.
Otherwise, I find with minimal base gasket (.2mm) and a little from the roof of the exhaust, this builds a very usable torque motor that will still rev well.
I'm not going back to a narrow inlet jug.
Also Deck height on these jugs seems to be perfectly matched to the 40mm stroke, with a 0.2mm base gasket, and standard head gasket, I get perfect squish without any messing around.
 
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frank66 said:
its allmost the same.

try exhaust port at 24 -25mm down from top of jug and 24mm wide.

transfers at 33-32 mm down from top of jug and 24mm wide.

this is 9000 rpm peak power.
Click to expand...

since we dont want to mess around raising the jug and needing crank stuffers i recomend finding the coreect blowdown and ditching all that nonsense.
7-8mm is very common for a torquey 40mm stroke reed motor. i can go ahead and say the blowdown is the biggest reason performance is low dave . the stock jug has a very low blowdown of more like 4mm.
 
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dave i have some 40mm jugs here and i have seen maybe 3 different port configurations. 2 for sure anyway. the ports are 2.5mm/0.1" wider on the largest i have seen i think. i had one that had small ports..... i cant remember if the heights were the same sorry.
 
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i looked at thse jugs bikeberry has also, i was thinking the larger intake port along with the 40mm bolt pattern would sure make setting an engine up with my new 20mm Mikuni carb a lot easier.

I also found a dealer here in Dallas Texas that sells the jugs that have the 35mm intake spacing, they look to have larger than normal ports also.

what is bad is that so many of the sellers dont list any specifics about the jugs they sell, I've ordered a couple that showed a jug with nice big tranfers in the pic but when I got the jug it is just a run of the mill jug with all the ports being tiny.
 
Yeah.. a lot of vendors do steal pics from other vendors making it really confusing to who has what... What appeals to me the most about the 40mm spacing is that it's a LOT easier to make intake manifolds that match a wide port job. You can make nice big ports on the 32mm jugs but there's the bolt spacing limiting you to how wide you can go and still bolt a matched manifold to it.
in an extreme case you could install aluminum bolts into the holes with red locktite, cut them off flush then re drill and tap them out further but that can be a hassle drilling since the aluminum bolts are high grade aluminum and the drill bit can wander to the path of the least resistance... it can still be done but needs to be jigged up and gotta use a drill bushing to keep the bit from wandering. Another way to do it is make a flange out of 1/4" thick aluminum and then install with countersunk screws with studs coming out from the other direction... still a lot of work compared to having a jug with the wider spacing to start with.

What I think would be really helpful is if the vendors would take a picture of the inside of the jug so we can see which ports they're using. The slanted transfers work ok, but not as easy to cut and modify as the flat across ones...

When we're talking blowdown, the flat transfers definitely make it easier to add blowdown since it's the exhaust port roof and the transfer roof hight that comes into play, but there is plenty enough room to add at least 3 more mm if not more blowdown.

Looking at another jug I got over here, there's also room for aux exhaust ports but one side would be very tricky to cut out, the other side could be drilled from outside the exhaust port but the one side would have to almost be done completely from inside the bore. This wouldn't add blowdown percentage, but it would help bleed off the exhause pressure from the cylinder faster for a similar effect.

I'll get one from BikeBerry to see just what they got, but if it's not what I'm expecting I may need to get one of yours.
 
there is only one cnc 40mm manifold and its for stock carbs. there is maybe only one way to mount a walbro aswell. dont get your hopes up. i recomend a 40mm jug and cnc manifold for stock carby....OR a pk80/rse....

Are you going reeds? cause 31mm PK80 would be better for the rse kit. atleast it fits in good in the pk80. it is alot of work if its a gt5 cylinder.
 
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RSE has 2 different sized reed kits, the one for a 40mm inlet has a larger 4 petal reed (DLE55?), and in my opinion is much better suited to a 66cc than the pissy little DLE 30 reed from the kit to suit narrow inlet jugs.
 
I just installed a 40mm intake jug from bike berry on my 40mm stroke motor. I cleaned up all the ports and it seems to work good. Although I'm still seating the rings so I haven't rung it out yet. I say go for it. Also the jug I got has big transfers but they are angled just a bit.
 
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