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It's on like donkey kong (117cc kit)

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Just got done placing the order. I started to do it last week but needed to speak with Mike at TB's a little more to see what he though etc...

So I've got the Stroker Kit 5 coming.

Race Cam for Race Head (since the 70 head flows better).

HD Auto Clutch

Oil Cooler

High Volume Oil Pump

New 26mm Mikuni Carb

Trying to find someone legit to do the case boring as soon as I get the engine apart. I'm thinking I might stay in the mini industry instead of taking it to a machine shop. We'll see...

Also thinking about lightening the flywheel - and just making sure I always roll it on instead of just whack the throttle (so the clutch doesn't come apart).

I'm excited about this and plan to take photos and do the whole thing up feature story style. I've already talked to a former 125 SX Champ and he said he'd love to ride the bike... so I plan on doing that with him. He's a factory rider for one of the mini companies, so that makes it that much cooler.

I'm just going to leave the bike's chassis semi stock to start with. This is allllll about the motor!

Any suggestions?

Mike

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Ohhh you know what. I forgot to mention the best part. I'm so stoked it's unreal. Like a little kid on Christmas!

I've got RM's, RMX's, CR's, CRF's all kinds of race bikes... yeah so what. I'm so stoked about building this cool little mini that it's unreal! hahaha

Jetster - I looked at those cases and considered it. I saw where PRC only charges $70-$80 (that price includes return shipping) to bore cases. I thought I might send it up and let them also do the flywheel at the same time (lighten the stocker). For that matter, I need to talk to them. I might even let them do the entire build. Let them drill the HV Oil Pump, do the case boring, install the stroker kit etc, etc... might be worth it to know when it gets back I can just bolt it in and go.

Dude... you know you and Kurlon are pretty much the ones that talked me into this right?!!!

Let's see -

Cruise to the Bahamas, or trick mini.

Cruise to the Bahamas, or trick mini...

Cruise to the Bahamas equals sunburn and hangovers.

117cc monster mini = PRICELESS!

Mike

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sounds sweet man. Im in the process of building a 117 right now too. :thumbsup:

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You should let PRC go all out and do a nice port job on your head too. I'm going to send my cases and ignition and there going to build me a full 4 speed/manual clutch 128cc engine from for $1075.

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Jet - since you've got a 117cc kit - how long do you think the HD auto clutch will last under this engine?

Also, any suggestions on the gearing with the stock tranny? Right now I think I'm stock rear, with 1T less in the front. Maybe go back to stock gearing and see how it pulls it???

Guardian - sounds like a sweet engine. I know they're supposed to do good work. Theyv'e definately got some cool fab' bikes in their photos. The YZ85s with TTR125 motors in them etc... Have you seen their CRF/XR70 in the photos? Unbelievable, I think it's all KTM65 suspension or something... looks absolutely wicked!

CRF70.jpg

These photo links rarely work for me - so if not, just copy/paste the link.

Still if anyone has any suggestions. I want to do this right the first time and not have a handgrenade. I'm concerned about whether or not to do the flywheel (lighten it) with an auto clutch. Don't want to fry it the first time out.

Mike

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I cant forsee the autoclutch lasting to long, youll go through plates like mad, and thats as long as the basket doesnt explode. The only clutches I know of that will hold up is the TB Manual clutch with the billet basket, and either the Kitaco Ultra clutch or Takegawa Special Clutch, but there both over $1,000.

As for gearing, I run 15/35 and it seems to work great.

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who told you the 70 head flows better?

Five0 - a few people have told me that. I questioned someone at a very well known mini/pitbike shop and they said yes as well.

Do the 70s have bigger valves than the 50? If not, possibly different porting?

2001 XR50 = CYLINDER HEAD

12200-GK4-761

2001 XR70 = CYLINDER HEAD

12200-GB5-931

XR50 VALVE, IN.

14711-GK4-013

XR50 VALVE, EX.

14721-GK4-601

XR70 VALVE, IN.

14711-GN5-913

XR70 VALVE, EX.

14721-GF6-010

Def different part numbers on the heads and valves.

Clue me in if there is a mistake, I'd like to know.

We're building two bikes, so we ordered a cam for Stock Head and a cam for Race Head to try with HD valve springs.

xxxxxxxxxx

Jetster - bummer to hear that. I was hoping to keep the auto if at all possible. I dig that about the pitbike - makes it... well a pitbike! LOL

I might have to go back and get the manual clutch, billet basket and would I need the upgrade plates - or are they part of the new clutches? I saw them on the TB site but I'm not 100% certain as I was looking at the auto clutch for the 70cc bike more...

Mike

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As I looked on tb's site, they say they have a reworked head now that comes assembled and with bigger valves. I think that is essentially a 70 head just with some work done to it.

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from what ive been told -

XR70 - 19mm/22mm valves

Old TB - 20mm/23mm valves

New TB - 22mm/25mm valves

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Actually it goes like this.

xr50 head-19mm/16mm

Xr70 head-23mm/20mm

Old Tb Head-23mm/20 mm but better porting design than xr70 head

New TB Head-25mm/23mm, larger valves, new valve angles, and updated ports

As for the TB Clutch, yes, they come with the new plates already installed, the update is simply to upgrade the older 2plate style clutches to 3 plates.

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yea dude theres no way a 70 head is better than any race head.

Stanton, I believe you read his original statement wrong, he ment that the 70 head flows much better than the stock 50 head, not the 70 head better than the TB Racehead.

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Actually we're looking at the race head kit too with the new valves. Dying to try it... but right now we thought it'd be fun to just upgrade what we have and then get the head later.

I saw the billet basket for the manual clutch looks sweet. I like that the ratio is changed with the manual clutch too. I was hoping to keep it auto because despite it being mega fast this way - I do have a niece that is in her 20s that rides the XR70 all the time while her husband and I are out riding. Guess I better start looking for something else for her to ride LOL

I've already ordered the HD Auto clutch, so I'll install it. Then after breaking the motor in, I'll see about ordering the manual clutch - I hear the guys at PRC have had great sucess with big bore auto clutches - bet it's one of the $$$$ auto clutches that are out there though. I'm not going to put more into the clutch than the bike is worth.

I can't figure out how the auto clutches aren't up to par yet with the pitbikes. There are full mod KTM50s (60+ cc) that are putting out in the 15-16hp range and their clutches last for a relatively long time. That'd be really cool if we could get a good three shoe clutch out of one of those things to work on these engines! Maybe the torque would still be too much - I dunno.

Thanks for all the heads up - any other comments let me know. I definitely want to hear the "whats what" before we start building these things.

Mike

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The problem doesnt really come from it being a autoclutch so much as the problem that the clutch is mounted on the end of the crank shaft. Its RPM's and vibration that destroys the cast basket and it eventually explodes. The only clutches that survive are the TB Manual with Billet basket as its strong than cast, that or the $1,000 clutches that move the clutch basket onto the primary transmission shaft.

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