100cc DD conversion to 116

twostroketoowoke

twostroketoowoke

Member
I have access to a ton of modern pre-2000 reeds and rotaries (ATK, ItalSistem, Titan, Sirio etc) in Europe that are in great condition or fresh from the builder that are less than $600 shipped. I’m aware of the cost to convert to a good 116 for indoor or bullring tracks but what is needed to get a crank long enough for a belt driver? It’s literally a nub hanging off for a DD chain driver but I know this is a “thing” that’s always been done to get Italian 100cc reeds/rotaries ready for 116 dirt use. Two mag halves? Welded extension shaft?
 
My DAP T85 custom conversion bolted right on the PTO stub like the DD pinion did...no extra length needed. I custom machined a core like Hegars to match the taper I needed, 9.75° IIRC. Saved a ton of lapping. But in terms of dimensions, it was the same as the Hegar and used the nut that comes with his cores.
 

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Just be aware any extra weight will be bad for the crank unless you use a 3rd bearing. i wouldn't weld anything at all because it is not easy to make a perfect job and that will cause vibration and eventually brake the crank. On most European engines you can use drivers and/or even extensions like the ones from Hegar. I have a bunch of them but run most of them with a chain. There are several people running these kind of engines on enduro laydowns and sprint enduros with belts.
 
Phiefer has made a gear that will go directly on and you can have an extended nut that goes through a third bearing support. Who ever you have build the engine should be able to make that for you.
 
Ted Hamilton said:
My DAP T85 custom conversion bolted right on the PTO stub like the DD pinion did...no extra length needed. I custom machined a core like Hegars to match the taper I needed, 9.75° IIRC. Saved a ton of lapping. But in terms of dimensions, it was the same as the Hegar and used the nut that comes with his cores.
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I need one of those for my T85.
 
My whole thoughts on this was, I can get a late model pre-2000 rotary or reed fresh from europe for little to nothing. The apex predators of the 100cc air cooled series. Once in my hands I can have it sent off to turn it into a 116 or superstock gasser for really small bullrings. But after talking to a few of you it brings my hopes up knowing a hegar or phifer belt driver will go right on the outboard shaft if it’s a reed or the inboard if it’s a rotary. Even taking a stock bore and stroke modern 100cc reed or rotary and adding some squish/timing/alcohol would be a potent indoor motor so I thank you all for the answers. The only issue IMO would be finding headers for oval pipes. All of them are sold with no header or a direct drive header.
 
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krtrcn said:
I need one of those for my T85.
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I too am thinking of jumping on that T85 train. That’s a hard price to beat and I believe they’re mid 90’s and have good ports? I can find homologation papers on just about every reed rotary that existed from the 70’s to early 2K but but not the T85.
 
Twostroketoowoke,

If you can't find a source, and need a belt pulley machined to go up tight to the case (like in the photo Ted posted), just let me know. Happy to do it for you. As Ted mentioned, many of the Italian cranks I've measured seem to be 9.75 degree per side -- why the heck they did that, who knows??

In the past (many many moons ago) when I road raced a KT100 (and with an axle clutch), I put together a crank with a modern tapered shaft ignition side, and a very old style straight-shaft PTO side. Then I just machine up a belt pulley that sat almost up against the case to get it as close as possible to the bearing. Beefy crank, and tight to the bearing worked out as a great combo.

PM
 
Allso, FWIW, those t85's are part of the Euro5 spec. They have 5 ports instead of the more modern 7 transfers, and thus have some built-in "limitations" that can be creatively massaged, probably. But for the price, you get a Selletra ignition, and great package. Here's what comes in the box, assuming it's the same package I got from Grand Products a while ago...I always have liked redheads...
 

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Ted Hamilton said:
Allso, FWIW, those t85's are part of the Euro5 spec. They have 5 ports instead of the more modern 7 transfers, and thus have some built-in "limitations" that can be creatively massaged, probably. But for the price, you get a Selletra ignition, and great package. Here's what comes in the box, assuming it's the same package I got from Grand Products a while ago...I always have liked redheads...
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Oof. Thanks for the info Ted.
 
Ted Hamilton said:
Allso, FWIW, those t85's are part of the Euro5 spec. They have 5 ports instead of the more modern 7 transfers, and thus have some built-in "limitations" that can be creatively massaged, probably. But for the price, you get a Selletra ignition, and great package. Here's what comes in the box, assuming it's the same package I got from Grand Products a while ago...I always have liked redheads...
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Do you have a picture showing 7 transfers and then what type exhaust ports does this engine have
 
nobozos said:
Some of the older 2stroke headers are interchangeable wouldn't be to difficult to duplicate. later Chuck.
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Some as you say, but not all. The headers from my PCRs won't fit most of my IAME engines. And some will fit but hurt performance since exhaust port is different shape.
 
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