Home Forums Shifter Karts CR80/85 Tech Talk

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This topic contains 41 replies, has 13 voices, and was last updated by  Gary Smith 1 month ago.

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  • #9964

    Derek Lodato
    Participant

    All former or current 80cc/85cc Shifter Drivers, Mechanics and Tuners. This topic is for us to discuss tuning, maintenance and performance of strictly the 80cc\85 class.

    I’m new to shifters and chose a New CR85 package from Alden Engines so I welcome advice on tuning, tech tips, performance modifications and maintenance on the 80cc/85cc packages.

    Any and all advice on best place to buy parts to fine tuning these incredible machines would be welcome

    Let’s get these 80′s back out on the track

    Thanks!

    #9989

    Gary Smith
    Participant

    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

    #10015

    Derek Lodato
    Participant

    @ Gary. Thanks for your input. I’m located in Florida and will be running a CR85 package for Sprint only.

    I plan on running a K&N style air filter. I believe the straights are about 600 ft at my main track.

    My engine is modified by Alden Engines. When I change the top end would I need a special heavy duty top end kit or could I simply replace it with a top end kit from Honda OEM?

    Thanks Gary

    #10091

    Gary Smith
    Participant

    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

    #10093

    Derek Lodato
    Participant

    Thanks Gary… I appreciate your input

    #12600

    shaun s noll
    Participant

    i’ve heard the cr85 pistons last longer for some reason.  i have two cr80s that i run, one swedetech setup from years ago and then have a woltjer ported cylinder that has ports WAY bigger than the swedetech or my other project X ported cylinder.  I always run the upgraded wrist pin bearing and woltjer pistons from Fastech (jon is the man and always helped me out, highly recommend ordering from him)

    always been curious how many hours you guys run your pistons before rebuilding them?

    #12607

    Gary Smith
    Participant

    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

    #12926

    shaun s noll
    Participant

    WOW!  is that a cr80 or cr85 Gary?  I had been told 3.5-4 hours on a piston was the lifespan for these built shifter kart cr80s so if you are getting >10 then I am wasting tons of money and time on pistons!

    #12929

    Derek Lodato
    Participant

    @ Shaun – This is a great question. I purchased a New Alden CR85 Engine with only break in time on it. I attempted to get a hold of Harry Alden but I heard he isn’t easy to get a hold of these days. My question to him was going to be “How often do I need to change out the Top End and Bottom End?

    I have heard many opinions on this. The engine I bought is said to put out 29hp so my guess is I will have to change out top end quite often but the seller said I should be able to get 8-10 hours on it. I have heard as low as 3-4. Still I am not certain. Anyone out there experienced with 80/85cc want to shed some light on this question for me?

    Is there a sudden drop in power as a early warning sign or should I just remove the head to look for signs there after 3-4 hours of run time?

    It would be MUCH appreciated. Also, any good builders out there you recommend to perform the engine work?

    I have been told that I could learn to do the top end myself – is it super difficult?

    Thanks again,

    Derek

    #12955

    William Martin
    Participant

    Top end rebuild is straightforward…not necessarily “easy”, as it takes some care to get it right. You will want a flat plate with a slot in it to slide under the piston so you can pull it down to the plate, helping you not twist the connecting rod while you extract the wrist pin. You really need a pin puller, but it can be removed by heating the top of the piston with a propane torch until the pin can be pushed out with “very little” side force on the piston. Never force it…that’s how rods get bent. When you have the old piston removed, use it to push your new ring into the bore about a half inch down the bore. Measure the end gap of the ring (feeler gauge), make sure it is within the specs that should be on the paper that comes with your replacement piston/ring/pin kit. If it’s too tight you might have a ring “stick” when it gets hot. If you don’t have a tool to insert the new clips in the piston pin bore grooves, be really careful not to nick up the piston or shoot the clips off into space…it is tricky. Pay attention to the markings on the piston top so as to get the new one in pointing in the right direction. Put some of that gooey pre-lube oil on the wrist pin bearing prior to reassembly, as well as on the piston skirt. Keep everything very clean, including your fingers while you do this work! Put a non-fuzzy towel over the open top of the engine crankcase, no extra stuff wants to be falling in there. That’s all that comes to mind…if you already knew all this, apologies for boring you…if I left out anything important, someone should feel free to chime in here and add information.

    Good Luck,

    Bill

    #12999

    Derek Lodato
    Participant

    @ Bill … Thanks…That is the most descriptive response I have heard to date! I greatly appreciate it

    I definitely want to work on this but most likely I’ll shadow someone during my first round

    Check your inbox

    Thanks again Bill

    #13029

    Gary Smith
    Participant

    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.

    #13391

    Carlos Perez
    Participant

    Hi guys! I am new to shifter racing. I should’ve got into shifters before, I love it! It was a big jump from a clone to a shifter! LOL.

    I have a 101 question that I have no idea: What makes a “modded” engine? What do I need to look for when I open the engine? I haven’t done it yet.

    The reason I am asking is because I was practicing at my local track and one of the guys there asked me if it was modded because it sounded louder and different than others. My local track rule book states that I should run stock 80/85 cc’s.

    Any pointers are appreciated!!

     

    #13394

    Matt Dixon
    Participant

    My guess is the silencer needs to be repacked, very simple to do.

    As for want to look for when opening the top end is any scratches on barrel wall, blow by on the piston , not sure if you can with an 80 but look at lower rod bearing.

    #13454

    Gary Smith
    Participant

    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

    #13574

    Carlos Perez
    Participant

    Thanks Gary! That’s exactly what I was looking for.

    Cheers.

     

    Carlos

    #19220

    Curt Smock
    Participant

    SOUTHERN INDIANA RACING ASSOCIATION runs this class as exhibition. I just got my son a Top Kart and a CR80 to run it next year. Lacking a lot of little parts. Motor Mount, carb, J-arm, pipe, fuel pump (same as clone?) Front drive gear with C clip. anyone have these or know where to look?

     

    #19222

    shaun s noll
    Participant

    i’ve got a bunch of extra stuff laying around like mounts, pipes, etc, PM me your phone number and I’ll make you a good deal

    #19248

    Curt Smock
    Participant

    PM’d you my # Shaun. Thanks. I hope to hear soon. I need to get this stuff ordered

     

    #19771

    john Dillon
    Participant

    Derek. Have you had it out and running yet?

    #22438

    Derek Lodato
    Participant

    For all of the 80/85 guys I have a question I have not found the answer to yet:

    Which pipe do you prefer and why?

    RLV TC4

    RLV TC8

    I will be running at a mid sized track. I’m looking for a good amount of bottom to get out of tight corners but I also want the mid and some high .. for straights and sweeping turns.

    I am from Florida so my main tracks are Anderson Race Park and Ocala Grand Prix

    Also, what brand and size silencer is best. I am looking at the Alden A3 and M4 but not sure size etc.

    Thanks everybody!

    Derek

    #22928

    Rod Balding
    Participant

    Need a starting place for jetting a Mikuni TM-28.

    Stock CR-80 with K&N
    Older RLV K-4 pipe and 12 x 3 M-4 silencer
    VP-110 / Burris Castor @ 6oz. to gal
    Altitude – 750′ Above Sea Level
    Ave temp 85*
    Ave hum 80%

    Thanks for any help .

    #22929

    shaun s noll
    Participant

    I’m not claiming to be an expert but the way I would do it is set the clip in the middle and probably start at 195 main jet and go from there with air screw 1 turn out or so.  Then adjust the clip to get the mid throttle you want and tune the main jet by running the motor at full throttle then immediately shutting it down and looking at the plug.  That’s the easy way to do it imo and once you get more comfortable with how they are supposed to run you can do it more by feel.

    I always have ran redline oil at 25:1 for what its worth

    if you google around there is a mikuni manual on how to tune these carbs, if you stay on the rich side they are pretty damn tough motors.

    good luck!

    #23034

    Rod Balding
    Participant

    Thanks Shaun , I haven’t ran them yet , but I’m close to your suggestion with 200 main to be on the safe side and you are correct , they are tuff little motors.

    #23067

    Dave Holstein
    Participant

    Does anyone know how to obtain the IKF specs/rules for 80cc?

    I have looked at the IKF site so long my eyes burn…

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