MxDad, I'm not saying this to get into a pi$$in' match with you. I'm asking so I might know what to look for. Everyone here has concluded that the stock shocks, while pretty, aren't all that great (my son has Works on his LT50 and that was one of the first things he noticed - how stiff the suspension is on the MX90). You apparently have cooling issues; I started with Engine Ice from the get-go and haven't had any problems, even riding mid-afternoon, 90+ degrees and very high humidity. You mention tabs breaking off in the same phrase as the under-sized radiator comment. What tabs are you referring to? The radiator mounting tabs? Body mounting tabs? I'd like to know so that I can inspect and weld up before I have the problem. You haven't mentioned any motor issues outside of the under-sized radiator and the only other issue was shocks. Oh yeah, you did mention the swing arm. I gusseted mine before I ever started the motor and haven't had any problems yet. Can you be more specific on the short-comings of the MX90? You say that you have put an additional $4,000.00 into the MX90 and it still is no better than stock. What all have you had to fix and what upgrades have you performed? Performance issues can be fixed with cash. Engineering issues need insight. Appreciate any info you can provide.

 

digginfool the tabs i was refering to are where the mud screen bolts bolt into the radiator they broke away from the radiator itself. I am on my 2nd frame 3rd radiator, 2nd swing arm all new shocks now. New steering stem, bars wheels ,axle A-arms are bent due to saturday The motor has been completely re worked port polished new head piston, reeds,carb,pipe,clutch the only thing that hasnt been touched is the plastic. 3 cranks all the way out to the kick start spring which is partially due to my daughters riding style which were working on when shes on it. I understand this is not a cobra but just now are they saying its for the novice rider when they first came out they never once said that. That whole apex web site has been changed since they came out but you must have just got one from them. My daughter is 48 pounds and 8 years old. She is very aggressive rider and has been racing awhile but with that in mind how could a 60-65 pound aggresive rider get by on these if she is hurting them. Greg at Apex is campiagning that they have race these just the way they are for a while now with that in mind who and what could they possibly be racing. We are gonna try the dirt track nationals on this thing in June so hopefully it will find a home there. The only place i have been satisfied with it is flat track and that is the only race it stayed together for and she took a 1st/1st in the 90 Jr class. It may be i just happen to get a lemon but you think they (Apex or Eastside now West coast) would have tried to make it right knowing my daughter was out campaining this machine at a national level. The machine is not what it was made out to be and they are not a respectable company. Pittman racing who sponsors my daughter on her cobra would never not make something right or correct the problems on a machine that are obvious flaws and there just a dealer. So i guess its machine and company that got me going nuts but oh well good luck with yours.

 

mxdad , where did you get your 2nd frame? what happened to the 1st one? why three radiators? and three cranks?and where did the aarms bend? we're racing this weekend and its going to be in the 90s here, this will be the hottest weather hes raced this quad in,i will sure let you all know what happens, it has no wiring other than kill, no dummy light for over heat ,im going to put a mechanial temp gauge on "soon", has your daughter broke her tranny gears? and how does it run now with the porting and other mods?

 

kasea 90 i got the frame from quad central it broke right behind the gas tank towards the seat. radiator first and second broke at those tabs where the mud screen bolts in bought 2nd one the welded it once i got it then the whole back side split on the second in the process of getting a different radiator to fabricate on off a dirtbike. As for the porting and polishing with the new head and piston it made huge differences it is still legal but the gains were huge. As for tranny gears im waiting on a set right now that will be her 4th i hope to have them for our race on saturday and sunday. she is flat tracking it both days at a county fair race and mxing her cobra in the day im to hesitant to take it back out on the track. Her new swing arm and suspension is from quad cental motosports as well the swing arm is plus one and 12 inch eyhe to eye on the suspinsion with there shock it rides like a cadaliac in the rear put elkas up front but she hasnt used them yet. Her a-arms bent at red bud when she blew the front shocks out saturday the lowers on both sides tweaked about 2 inches from the frame. The cranks are her fault because she hasnt got complete hang of getting out of the gas when jumping and on whoops she cant double in and out of the whoops on this machine without keeping the throttle pinned it doesnt have the power. We are currently working with blaster boys motorsports on tryiing to come up with some sort of power valve for this motor which would help it keep power alot.

 

I guess there have been changes because there is an overheat light on my son's MX90. It does work because he did get it to turn on once. He got the quad high-centered on a clump of sawgrass and was trying to get it off by gassing on it and rocking the bike. It took me a minute to get back to him and the red light was on when I got there. We had been riding the airboat trails really hard so I know the engine was already good and hot. K90, try using Engine Ice. I'm in Florida and we've had no problem with overheating yet. Greg at Apex has said he is trying to find someone that can provide an electric fan for the radiator. It's more weight, but if it keeps the engine cooler, you can safely get more power out of it. MxDad, why the new pipe? This pipe looks identical to the pipes that are offered for any of the other scooter-engined quads (don't patronize me with looks can be deceiving - this is an honest question). Did the stock pipe break or was there a performance issue and whose pipe did you use? Who did your engine work and what size carb did you go to? I do have a problem with my carb right now. It doesn't have any idle adjustment. The idle adjustment screw doesn't touch the slide until it is almost completely turned in and then not enough to make a difference. The only way I've been able to keep the idle speed up is to adjust the throttle cable until the idle speed comes up but then the idle is erratic. It appears to be a Keihin PWK carb in every way (including the PWK on the float bowl) but I would expect crisper throttle responce from a flat slide carb than I'm getting. Power seems to go flat at WOT with the 92 jet but loads up on the mid-range with the 95 jet. Experimented with needle position but didn't help with the mid-range bog. I might go down and try the 90 to see if that helps overall throttle response but I don't see how that is going to help my top end. Any tips? The other thing is the radiator. I looked at my radiator and the mud screen mounting looks fairly substantial. You speak of tabs on the radiator but on my radiator there are welded lugs the bolts thread into and the tabs are on the mud screen. It looks like a substantial enough mount for the weight involved. What kind of bumper are you using? Could it be that the bumper you have is not providing enough protection for when your daughter gets underneath another quad? Just wondering if our quads are that different or if there is another issue at work.

 

digginfool the welded lugs that the bolts go into are what is coming apart we have a AC front bumper which offers more protection than the stock one BBM did all of the motor work went with a Hetrick pipe for personal preference and it has worked out alot better. Instead of playing with your jets check your intake gasket i have been through that let it idle then spray aroind the intake gasket and see if it dies. This was my problem and i thought it was jets but it was the gasket. We are running a 28mm carb. Today alone we went through 2 sets of tranny gears one in each moto something is wrong internally the clutch play in it which should not be there And for anyone to tell ya they interchange parts with certian other minis the gears are same style and polaris but they will not fit in 2mm differnce on the inner gear. Also with the 24 that came on hers we ran a 115 main jet

 

well we raced sunday and son took a second in 90mod "a"heat race, witch is a 2nd overall they ran a,b,and c together, but in the main 2nd lap the chain broke , he was in 2nd again , but he had a good time and rode a track he hasnt raced before,but i can tell you he was flying , in the heat race after 3 laps "the track was over a mile" they were coming up on lapping others, so over all the aasco did good as it could do, also saturday in practice the quad started sputering and i was getting shocked working on it "weird" the fix was to put a ground wire from motor to frame , it fixed it.

 

mx dad when are son broke his gears last, i put in kasea gears from hetricks, same ,other than a clip instead of nut, and i know a few people that have went through four sets in four races, the kid wont let off the gas in the air, my son has it down, hes only been through two sets,on two quads in a season and saturday kids were burning up clutches, other than the chain witch was new we have been lucky , the chain was a really pisser.

 

Hi I have been reading your postings. My son is racing a promx 70. We changed the shocks to elka but that is all we have changed. Its been a pretty good quads for him because this is his first year racing. But we have fouled a lot of plugs though any help? And i see you guys talking about something ice. Is that the coolent you use? Sorry for the dumb question but like my son this is my first year racing to. And you guys keep saying scooter engines. Why is that? Thanks again for your time

 

The product is called Engine Ice and yes, it is a coolant. It is rather expensive but it does work well. Except for the Honda, Cobra and a few other purpose built race quads, most of the youth quads are built around engines and drivetrains that were originally designed for scooters. The next time you see a scooter, take a good look at it and then go home and look at the set-up on your MX70. You will see that where the front sprocket is, that is where the rear tire would mount on a scooter. Nothing wrong with the setup as long as the engine and tranny is durable enough for the application. If you are fouling plugs, you are running too rich or running too much oil. Make sure you are using a proper fuel/oil mix first. If that doesn't clear up the problem, try dropping your main jet one size. You probably received three jets in addition to the one already installed in your carb. The size is stamped on the side of the jet. Pretty easy to change. Remove the carb, open the float bowl and the jet will be right there in the middle. Remove the existing jet, read what size it is and then install the next smaller size. Do not overtighten or cross-thread as you can strip it very easily. Re-install the float bowl, then mount the carb back on the bike. That should help.