$350 ported 5mm stroker engine - Port specs added- please give advice

[Schmidty721]

Please see post 16 & 18 and give me your opinions on this set up.

EDIT: Engine is not for sale. $350 is the price I paid.

I purchased the 62t/61x engine mademan9 had listed for sale not really knowing what I was getting. I needed a head and 61x cylinder for my current build and the price was right so I picked up the complete long block with dual 38's, carbon reeds, intake spacer, flywheel and a couple other little things.

Pulled the MRD girdled head off and see it has the domes cut back ~ 3mm.
Pull the cylinder off to and find an aftermarket crank. Per my measurement, it is a 73mm stroke. Cases are fully ported and epoxied. Cylinder looks to be re-sleeved with minor port work. Sleeve ports match the cylinder ports perfectly. Bore is 81.5 mm and both cylinder and pistons appear to be in great shape.

I spoke with a previous owner (not the engine builder) and he confirmed it was a stroker crank, but was unsure of the size. He claimed it came from a racer in California that rode for Yamaha. It was rebuilt with a new crank, fresh re-sleeved cylinder and top end with about 2 hours total on it. Orginal setup suposidly ran fuel injection and the orginal builder recommended he run a set of dual 46's... that ALL i know so far.

I need the experts help here. What the hell do I have????

 

[Schmidty721]

 

[Schmidty721]

 

[chriselmore_1]

if your sellin it for 350$ I'll take it

 

[Schmidty721]

Engine is not for sale. $350 is what I paid for it. Sorry if I got your hopes up.
I'm just trying to find out as much about this engine as I can.

 

[Andrew1289]

Looks to me like a Rad crank.

 

[3rdgearpinned]

what you have is one HELL of a $350 motor!!

where did you find this deal?

 

[Tyler Zane]

dude, if i dont know schat i do know you got a good deal!

 

[Schmidty721]

From my research the RAD cranks were a 5mm stroker? This agrees with the 73mm stroke I guestimated using a caliper.

81.5mm bore * 73mm stroke puts this at 760cc with the option of going larger.

I'll need to purchase a different set of carbs for this thing. Any suggestions on what I should look for. Will a set of OEM 44's and stock intake do the job or do will I need something larger/nicer aftermarket?

 

[the WaTeRhAwK]

killer grab-bag motor...lol

 

[DangerBoy]

EDIT: Engine is not for sale. $350 is the price I payed.

I purchased the 62t/61x engine mademan9 had listed for sale not really knowing what I was getting. I needed a head and 61x cylinder for my current build and the price was right so I picked up the complete long block with dual 38's, carbon reeds, intake spacer, flywheel and a couple other little things.

Pulled the MRD girdled head off and see it has the domes cut back ~ 3mm.
Pull the cylinder off to and find an aftermarket crank. Per my measurement, it is a 73mm stroke. Cases are fully ported and epoxied. Cylinder looks to be re-sleeved with minor port work. Sleeve ports match the cylinder ports perfectly. Bore is 81.5 mm and both cylinder and pistons appear to be in great shape.

I spoke with a previous owner (not the engine builder) and he confirmed it was a stroker crank, but was unsure of the size. He claimed it came from a racer in California that rode for Yamaha. It was rebuilt with a new crank, fresh re-sleeved cylinder and top end with about 2 hours total on it. Orginal setup suposidly ran fuel injection and the orginal builder recommended he run a set of dual 46's... that ALL i know so far.

I need the experts help here. What the hell do I have????

you have an old school era 1996ish stroker
standard set up was heavily ported cylinder oem (0,0 were hunted for), tunnel ported cases Rad 5m crank ($$$)
pistons come up out of the hole so they require a special head
most used MSD total loss ignitions with lots of advance and GRE Green Racing carbs or msd fuel injection, and lots of compression, these motors turned lots of rpm

these were predecessors to the taller aftermarket cylinders that allowed for 6mm stroker long rod motors

Db

 

[Schmidty721]

you have an old school era 1996ish stroker
standard set up was heavily ported cylinder oem (0,0 were hunted for), tunnel ported cases Rad 5m crank ($$$)
pistons come up out of the hole so they require a special head
most used MSD total loss ignitions with lots of advance and GRE Green Racing carbs or msd fuel injection, and lots of compression, these motors turned lots of rpm

these were predecessors to the taller aftermarket cylinders that allowed for 6mm stroker long rod motors

Db

Thanks, this is the type of info I was hoping to get.
The rods have 82m stamped on them. Is this an 82mm rod? What is stock rod length?
Am I wasting my time trying to set this up as a free ride motor? The cylinder porting doesn't look too drastic, but I not an expert by any means. How much does case porting affect where to power hits?

 

[DangerBoy]

OK this is making my head hurt thinking this far back, without notes, on a Sunday , after a margarita

stock length yamaha rods are 125 mm long later we used rods at 132 and 133 mm lengths
( one was a honda rod the other a kawasaki)


most engines of this era were built for closed course racing, as such they need some significant changers to become good free ride motors

most were set up for race fuel with high compression ratios

you say the porting doesnt look radical but
remember when computing the port timing, you MUST take into account the cylinder port height( measure to see if it was decked top or bottom) plus the amount the piston travels up out of the cylinder into your calculations minus any spacer under the cylinder

these motors started around 1991-92 with 6m6 cylinders and 61x cases with small ports and progressed from there getting better and better you have 62t cases hence my 1996 guess)

cranks by Rad or rebuilt by Falicon were the choice of the pros

no matter what, for 350 bones if the crank is good you got a good deal
I think crankworks will rebuild Rad cranks

also there were at least 2 versions of the Rad 5mm crank one being way lighter than the other

all this said, they are not plug and play motors, so depending upon your wants and needs you may want to use this motor to finance your freeride motor

Db

 

[BombThreat]

sweet deal man, i bought a boat with a motor that was very close to this. It ripped like a mother with the MRD injection and all but I wound up buyin a new cylinder and having that ported and installing some 46MM blackjacks. I paid $1700 for a mint complete race SN (built but never raced though)

 

[Schmidty721]

the crank seems mint. Super smooth with no noticeable play. Are there any markings on the crank that would tell me which one I have?
I measured the overall cylinder length, gasket surface to gasket surface, and it averaged 118.75mm. I also measured my stock 61x cylinder at ~ 119mm.

When the engine was together, I measured the amount the pistons came above the deck height to be ~ 2.3mm. The base gasket measured 1.1mm. I just remeasured the squish cut in the domes and that averaged ~2.6mm.

The numbers "61,43" are engraved on the top and bottom half of the cases on the coupler side. Any idea if this is a reference to the setup?

I'm guessing the port timing is based on cranking degrees? I'll have to read up on how to do this. We have degree wheels at work that I'm sure I can make work.

 

[Schmidty721]

I spent some time (port mapping?) my cylinder last night. Dimensions aren’t exact, but should be close. I’m working on an adapter for a degree wheel so I can get the port timing specs. Are there any standard practices to follow when doing this? ie. What is considered port open and close. My exhaust port has a pretty aggressive chamfer through the sleeve. Just wondering if “open” is as soon as the piston clears the opening on the sleeve or should I wait until it drops down further to say the top of the port in the casting?

I also have a set of EOM 44’s with stock manifold and stock F/A setup on the way. I know they’re not my best option but it fits the budget right now and I needed something larger than stock 38’s. Does anyone have a guess to starting point for jetting? It will be running a Coffman’s exhaust, pjs waterbox, MSD enhancer, cranking compression is 150ish I believe, Solas 14/18 concord. I do have a dual primer kit so choke plated are coming out. I checked out the carb spec data base thread but nothing was very similar to my set up. I’m hoping to get some jets ordered yet today for the weekend .

 

[waxhead]

Nice find and good buying
Very mild case porting but still a great base engine to start with

 

[Schmidty721]

So I finally got around to machining an adapter for my degree wheel and got the port timing specs for this engine. I used a .004" feeler gauge to determine when the port was "open". I don't know if there is a standard practice that is used or not, but that what i did. Port Map is attached in post 16.

Exhaust open: 89
Transfer open: 122
Exhaust duration: 182
Transfer duration: 116
Blow down: 33

I have a set of OEM 44's with stock manifold. I tapped the cases for a second pulse fitting. Does anyone have a guess to where I should start on jetting?? I finishing the engine today and its going in the ski!

I also have the choice of 61x or 62 electronics. I want to run the 61x do to the fact it already has my MSD enhancer installed and I know everything works correctly. Any objections to this?

 

[davidescu_radu]

how is it running?

 

[Schmidty721]

Funny this thread popped up again. I still have this engine, all though I don't have a ski anymore. I've run multiple combinations on this, with last being X-scream 46's, total loss, and a Speedwerks dry pipe in my old vision hull. It's been a fantastic power plant for me. It's been sitting for over a year. It's on my to do list to do a health check on the engine and total loss and get it listed for sale.