[Gary Smith]

As for balancing tires on a sprint kart, it depends on the tires. If you are experiencing a front end shake,  look at the front tires for balance and how true they spin. On occasion I’ve had front tires shake violently at and above 40 mph and once I had a rear tire take over 2 ounces(ran out of weights) to get any where near balanced.

It just depends on what you are experiencing, front end shake at speed, look for tire balance and trueness. Massive shaking on kart, look for the same in the rear.

Gary

#55 Honda CR80

[Gary Smith]

Kyle,

Call John at Fastech Racing, he should be able to help you out.

831-384-5278

Gary

#55 Honda CR80

[Gary Smith]

According to my service manual 1995-2007 CR80R/RB, the only difference is 5th and 6th gears in 2005- 2007 models.

I believe you are looking for the billet heavy duty 3rd gear, it should be the same in all years, make sure it is a 28 tooth gear and you should be O.K.

Gary

#55 Honda CR80

[Gary Smith]

I guess if I was to try this, I would use a Leopard carb, HL-334AB, although I would find it rather awkward reaching back to fiddle with the needles to tune on the fly.

In my opinion, I can’t see any thing wrong with the Mikuni TM28 carb. Once  you get the jetting down for the tracks you visit, it’s just a matter of watching the air quality and adjust accordingly. Of the 4 tracks I go to, I only have to change the jetting for 1 track, it is 1,500 feet higher in elevation, one step down on the main jet and I’m on my way.

Gary

#55 Honda CR80

[Gary Smith]

Hi Berkeley,

This has happened to me before, I’ll bet the stud that pulled out has short threads on one end and longer threads on the other end, with the short length of thread in the hub. These studs should measure aprox. 34mm long with 10mm thread length on the short end and 20mm length on the long end. I have found a 40mm long stud with 10mm thread x 8mm thread , drilled and re-tapped the hub, and every thing is good. I have a mill in my garage and able to keep every thing straight.

After this has happened twice, I now pull the studs out any hubs that I acquire, and replace them with  38mm long studs with 17mm thread length on each end. If the threaded hole is not deep enough in the hub I drill and tap them to accept the stud, of course using blue Loctite to finish the job once and for all.

Gary

#55 Honda CR80

[Gary Smith]

I buy used take-offs from my local kart shop. I have had problems in the past with severe front end shake without balancing. I now balance only the front tires with up to an ounce of weight, some tires take more weight, I stop at an ounce, not looking for perfect balance, just something close.

Gary

#55 Honda CR80

[Gary Smith]

Hi Ryan,

Do you still have the 2008 M32 chassis?

I would like to take a look at it.

Thanks

Gary

[Gary Smith]

Frank,

Kart seems to handle better since my brain took charge of my right foot. I have also gone to shorter rear hubs, positive caster and change from neutral camber to slight negative camber. Kart is now a little loose in, not as much steering input to snap it loose on exit.

Gary

#55 Honda CR80

[Gary Smith]

Greg I believe you are absolutely correct about the cracking along the intake port, the cylinder had been welded on 1 side already, cracked thru that weld and started cracking on the other side of the cylinder as well. Like I said, this ported cylinder was an extra offered in the purchase of “motor package with extras”. I put this cylinder on to see what it would do, unfortunately the ignition took a dump the same time I put this cylinder on. I was quite impressed with the performance gain, 1/2 second a lap and lots of rpms.

Gary

#55 Honda CR80

[Gary Smith]

UPDATE:

During the past 5 months, have tried many things to figure this out, turns out it must be the black box. It runs good some times, and other times runs like crap. I put on an old Vortex ignition box and ran great, then the cylinder cracked along the intake port, put on my other cylinder, ran great, changed back to the old black box, ran great, changed complete motor and after break-in, runs like crap again. The same thing, around 10,000 rpm it starts to flutter. New motor has different stator and pick-up, the only thing that is the same is the black box and coil. Have 2 spare black boxes, I feel confident changing that black box will fix the problem.

Gary

#55 Honda CR80

[Gary Smith]

TJ, I think it is driver related, I tend to mash the throttle coming out of the corners. I’m going to try to feather the throttle until the kart is in full control, then go full throttle.

Thanks for all your advice.

Gary

#55 Honda CR80

[Gary Smith]

TJ, you are correct, the tire is lifting when counter-steering. The rear width was at 54.5 inches, increased it to 55 inches when I widened the front, it helped but did not eliminate it.

Gary

#55 Honda CR80

[Gary Smith]

Carlos,

I think your question is ” How do I tell if I have a modded engine?”  correct?

Check your bore size, CR80 1986-2002 47.00 mm, CR85 2003-2007 47.50mm, any other bore size is not stock. You mentioned 101, check you bore, if it measures 52.00mm, it is an aftermarket 101 big bore kit. Check your rules, might still be legal. Another thing to look for is enlarged transfer ports, these are the 2 little holes in the reed cavity in the cylinder you see when you remove the reed cage. In stock form they are rather small, look like a reverse capital “D”, 7mm dia rod fits snug, quite frequently they are enlarged. Also if your head has “O” rings rather than a gasket, it has been modified. Check your rules as what is termed “stock”.

Gary

#55 Honda CR80

[Gary Smith]

Shaun, I have 4 motors, 2 are stock, 1 is a 105cc big bore and the other is a modded cr80. I currently have 3.5 hours on the modded motor, and still running strong. The Honda  service manual says the piston and ring should be replaced at 7.5 hours with the piston pin and bearing being replaced at 22.5 hours. I figure the piston and ring can go a little a little longer than the recommended  time rather than the small end bearing. I have been running these CR80’s for 6 years and doing top ends every 11-12 hours with no problems with piston or rings. The ring gap after 12 hours is at the max of the service limit, which I feel is taking the parts to the limit. The only failure I had was at 11.5 hours,the small end bearing cage broke into 3pcs, but remained intact, no damage to anything. The motor was running fine, I only found out about the bearing doing my routine top end rebuild.

Gary

#55 Honda CR80.

[Gary Smith]

Shaun, I put about 12 hours on my top end when I replace the piston, ring, wrist pin and bearing. I’ve had one wrist pin bearing cage fracture, stayed together and caused no damage, dodged a bullet there!

Gary

Honda CR80 #55

[Gary Smith]

Yes, they are directional, mount them yellow side out on the right and black wall on the left.  Like Clark said, take it easy on the 1st session, let them cool, then your good to go.

Gary

Honda CR80 #55

[Gary Smith]

Well, this brings up a sore subject. I gladly threw my 2003 Biesse B3  away after only 25 hours on the chassis. It broke at the rear bearing hangers on both sides of the frame rails. Of course I stripped it of all valuable hardware except that vulnerable lower steering shaft bearing that would wear out after 3 hours of use and is different than any kart made. I did manage to retro-fit the 50mm axle rear brake assembly onto a 40mm axle kart.

Gary

Honda CR80 #55

[Gary Smith]

I’ve been doing a little research on these engines again , one of the things that turned me off was  the shift pattern, it’s all up, neutral on the bottom. When I was a teenager, I had a Kawasaki 350 twin street bike, that bike was fast. I hated the shift pattern, all up, when down shifting, once in a while you would go past 1st and into neutral. I know on my CR80, I only go into 1st when starting out or have a major problem on the track,  but I know I won’t hit neutral by going to far down on the shift pattern, just one more thing to think about.

Gary

Honda CR80 #55

[Gary Smith]

Larry, you hit the nail on the head, there is no after market support for these motors, that is why a Honda CR80 is a perfect package, there are motor mounts, #428 counter shaft sprockets, and pipes readily available. You can’t race this package, but who cares? I just want to bang gears and have fun on practice days!

Greg ,I’m an old guy also, my buds have 125cc Hondas, they try to talk me out of this 80cc junior crap all the time, I keep telling them, “How come you show up at work on Monday with all your aches and pains from karting? I feel fine, no problems.” I get to bang gears all day long, go pretty fast without the brutal beating of a 125cc shifter. As far as cost, I don’t see it, a properly running stock CR125 needs nothing more than a top end every 15 hours or so, for about $125, if you do the work yourself, and a bottom end every 50 hours.

Just my  2 cents

Been there, looked at it, went to Honda CR80 instead.

Gary

Honda CR80 #55

[Gary Smith]

YES!!!, it is a MUST DO!!!, if you don’t replace the stock 3rd gear it will fracture, taking many gears along with it and probably the counter shaft with it. I should know, it happened to me. Took out 6 gears and the countershaft, I quit counting dollars when I got to $400.

The stock 3rd gear has cut-outs that go completely thru the gear, which makes it weak. The aftermarket gear has cut-outs for dog engagement on the side that is required for engagement and the other side is solid, giving it strength. Never had an aftermarket gear fail yet.

You can get the gear at   sharkshifter.com, it might seem a little pricey at $112, but compared to $400+, and any other damage that could happen, it is well worth it.

Gary

Honda CR80 #55

[Gary Smith]

5 years ago, I had the same idea, luckily my buddy talked me out of it. He said “why try and re-invent the wheel, get a CR80” I got a CR80 and love it, parts are readily available, plenty of after market karting support, like motor mounts, pipes, shifting J-arm and counter shaft sprockets. A stock CR80 makes about 24 HP, I can keep up with most 125cc tag karts, but CR125’s kick my butt down the straights.

Good luck,

Gary

Honda CR80 #55

[Gary Smith]

From what I remember, a 125 clutch cable goes into the motor near the countershaft sprocket, on a CR80 there is a bracket that is attached to the right rear cylinder base stud. Do you have this bracket? It is called “Receiver, clutch cable” Honda part #22821-GBF-830.

Hope this helps.

Gary

#55 Honda CR80

[Gary Smith]

You can expect your rpms to increase 67 rpm per 1,000 rpm in each gear at the same speed. Just say with your present gearing you are coming out of a corner in 3rd gear at 8,000 rpm, changing to 15-25, at the same speed, you will be turning 8536 rpm. It will give you more punch out of the corner, but you will loose a little top end down the straight. Are you getting into to 6th in the longest straight? Are you maxing out your rpms in this straight?

Gary

Honda CR80 #55

[Gary Smith]

Derek, before you order any parts make sure you know if it is a CR80 or a CR85, the only difference is the piston and ring size. Both Fastech-Racing and Sharkshifter carry top end kits for both CR80 & CR85. The kits come with a heavy duty wrist pin bearing.

Gary

Honda CR80 #55

[Gary Smith]

Congratulations on your motor package purchase!

Just a few questions :

What type of racing?  Sprint, Road Racing or Dirt?

Where are you located?  Altitude for jetting

Running an airbox or open filter? again for jetting

I run sprint tracks with 700- 850 feet straights, I find that a 17 tooth countershaft sprocket and a 27 tooth axle sprocket work best for me. I run a K&N style air filter at about 800 feet above sea level, and my jetting is 37.5 on pilot jet and 195 on main jet.

I order a lot of my parts online, I find that  fastech-racing.com, and sharkshifter.com have most of the parts I need. Every once in a while I stop by my local Honda motorcycle shop to gets parts as well.

I hope you enjoy this motor package!

Gary

Honda CR80 #55

[Author]

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