drx90 bogging on low end?

[greenmachine70]

My sons drx90 is bogging on low end. Absolutely no holeshot. When you pin the throttle, it bogs down, moves slowly for 1-2secs then it picks up speed.
The carb appears to be very clean. I have adjusted it every way possible. I have a nice tan/brown burn on the plug.
I changed the air filter to a k&n with a foam prefilter wrapped around it. I changed the main jet from stock 105 to 115. That helped the top end a little. BTW, it is a Mikuni carb stock.
Could this just be the torque spring or rollers?
Please help...

[greenmachine70]

oh yeah, I am a newbie on here. Been lurking for some time. Thanks for all the great info.

[drr5]

is this an air cooled or water cooled? sounds to me it could be the carb,but tourqe springs may also play there part

[greenmachine70]

air cooled

[hotquads1]

I am with drr5 , is it an OKO carb? if it has been running well and this started suddenly the torque spring is suspect , this is an easy fix and good maintainance too , is the cvt setup all stock?
marc

[greenmachine70]

quad is totally stock.
it has a mikuni carb
I added the k&n style a/f with a foam prefilter wrap.
I also upped the mj to 115(to see if it helped)

[greenmachine70]

wihtout spending a bunch of money, i would lve to see this thing have the ability to pull the front wheels up. I am ready to change all the springs & rollers if that will do it.

How do you tell what size the carb is? I know it says Mikuni on the side for sure.

Thanks

[drr5]

what year quad is this? if its an 06 or earlier you would have the 16mm , if thats the case i would get an intake and an 24 keihn round slide,and change the rear tourqe spring, clutch springs, roller weights.

[hotquads1]

your quad should have the stock heavy rollers , need to lighten them up to get the revs up on the launch . but if want to do wheelies you will have to increase power dramaticalyy over your stock engine , I would do everything DRR5 suggested and put a pipe on it, the old style exhaust you have is limiting the power quiet a bit . 80 degrees in Fla now I would back up to the 110 main jet and put air screw at 1.5 turns out and see how it feels.
marc

[greenmachine70]

I bought this quad in late Nov. 2006 for last Christmas.
It was sold to me as a 2007.
It measures 41"approx. to the outsides of the tires with the shallow dish out.
It is all stock except for the air filter I previousley mentioned.
I also have a pair of 18x6.50/8 snow hogs to install later.

I know the carb is mikuni. I have not adjusted the needle clip yet.
This quad ran great from Jan 07- Aug.07.
What sprocket is working for fast trail riding with hills & soft FL sugar sand?
What rollers do I have & what should I have?
What springs would you all say are good for us?
Thanks for any info.

[bulldogfallon]

Rollers 4.75 to 5 gram


The needle setting is critical to these minis..


Your carb is small for a 90..


You may have a tired torque spring, flat spotted rollers,, and/or a carb that needs a little tuning

Have you changed your spark plug, even though it looks good?

You didn't mention that in the email you sent me....

[greenmachine70]

I will change the plug & repost. Thanks

[rider1234]

Same thing happened to me and I had to play with the air screw. I had to turn it in clockwise (richen it up). Only turn it 1/4 turns at a time and try to punch it. if it gets better keep turning and if it gets worse turn the screw the other way. I would start there. When this hapened to me I played with the clutch for a week and nothing. Just remember change one thing at a time, and if that was not it then change it back before you adjust something else. GOOD LUCK!!

[QuadJunkies]

We have LITERALLY done EVERYTHING there is to do and it still does not solve the problem ,its still hasnt corrected the flat spot. It cant even pull the gearing it should right now ..
We have exhausted every resource to get this thing off the line like the others. Brandon plays catch up eventually most of the time,but something is simply not right inside somewhere and theoretically it should.:confused:


My suggestions were what everyone else has already addressed so far.
Hopefully yours is just a simple fix since it ran great before this ! :)

[Steven623]

Did it run well before the K&N filter was put on? Always keep a log book on items that were changed etc...

[QuadJunkies]

What belt are you running?Ill go back and read again, but Im assuming it was the stock belt.;)
Check for belt slippage also..

[ecmini1]

Sounds like weak clutch springs, You said ran fine for months then this happened! Usally clutch springs.
This is a hard subject to resolve over the forum with to many other variables that could cause the same symptoms. There was alot of good info given to try and guide you in the correct direction just do one step at a time.

[dodgepower]

you check compression?....had that happen with us....changed out all the clutching and timing and wound up we were loosing the top end.................just a thought

[greenmachine70]

max compression i could get was 100lbs. I guess it is time for a cylinder/piston. Can you go with a bigger piston/cyl. & get any benefits without any other major mods?
Would I see a big difference with that alone?
Or do I need to do a bigger cyl/piston, intake & carb?
I am looking to get the most bang for the buck.
We dont race, just ride trails & our property & practice tracks from time to time. My son is 9 & can ride the wheels off this thing as it is. I am confident he could handle a bit more power. i know he would love it too.

All suggestions are appreciated.
Thanks

[bulldogfallon]

Dusty will take care of you...

You can tweak your stock stuff to get some power....

Local hands on help is the best

[Nichols Atvs]

Yup time for a top end .You can go bigger but it will not be a HUGE difference . mods would make a bigger difference ported cyl and cases and bigger crank or stuffer cran,k hi comp head and bigger carb. nothing comes cheap .

[hotquads1]

since you do not race , and you dont want to break the bank , you can easily upgrade to a 53mm alluminum Hi Perf cyl kit for not much money difference . You allready have to buy rings and gaskets at the very least, so this would be a good time to make the change . No labor cost - fairly easy do it yourself job , you can still run pump gas , and increase performance . this is one option and there are many more but cost can add up quickly , the sky is the limit.
marc

[jetski_dawg]

before you go buying a bunch of stuff.. make sure you have a good compression gage maybe borrow another to back up the one you have as being accurate.. second, make sure you didnt over-oil the filter..a little goes a long way and use uni-filter oil.. or put the old one back on just to test it

[dodgepower]

hey glad could help ya out.................good luck and bulldog and the others are right there are a ton of options you can do. alot of boils down to the pocket book.

[bulldogfallon]

Guys....He has the small Mikuni carb and retrictive exhaust.

I am sure that upgrading the carb and pipe along with fresh rings will be a great start..

The tranny could probably use a little love too(new springs, rollers)....Maybe lighten the flywheel too...notch the timing a little...


A bigger cylinder will not be as effective as it could be without changing the carb and pipe.....

Bring the 90 to one of the local DRR Nation dealers and I am sure you will be happy and still have some money left in your pocket.

I am going to try to make some of the FTR races in N. Fla, so maybe we can meet and talk ATV.....

This forum is a great source of info as well