Modding advice for a drz 125

Would appreciate some advice and reports on moding a Drz 125l

My son ( 11 ) was bought a drz 125 l in the summer . It's a great little bike and I am trying to look ahead to see what's the best bet for him in either improving this bike or suggestions for a different bike to suit when more advanced.

The drz does run lean it takes a while before you can shut the choke off .

So rejetting and a exhaust maybe in order here . The only mod I have done to this bike is to take out the spark arrestor and bolt on a billet end cap.

I don't want to go down the route of big bore kits , this will then tempt me into revamping the suspension . I am aware that you can bolt on a rm 100 forks and even change the swing arm . This all seems worth while but it then makes me question the economics of this . I could keep her near to stock with just a few mods to keep my lad happy for a year or two , then sell her and get something like a Honda crf 150 .This bike being a four stroke with all the "expert" bits on her as standard. The bike is also 3 kgs lighter to boot.

So that's my dilemma , any thoughts and opinions are most welcome.

To simplify my ramblings:

What are the easy mods for the drz 125 l ?

What's the next bike when he's 13/14 yrs old ?

Would a 2 stroke be a better move also ? ( only throwing a smoker in to the debate cause my lad is finding the drz 125 l heavy at the moment , being 80 kgs in weight ).


Open air box and put on a decent pipe will give u modest gains. 143 Big bore is not such a bid deal to do and with a 26 carb (ex ebay) you will be getting substantial gains. 190 kit and 28 carb HUGE gains.

Not really need to do swingarm but RM/CR/KX front forks not big deal if you pick up decent set off ebay and make a very big difference. RM best option because can use DRZ brakes and wheel.

Rear shock ex CR85 again off ebay not too expensive.

Re next bike CRF150 is NOT lighter and does not have 'expert' parts. Heavy and slow. DRZ better. Perhaps you mean CR150R which is fast, ight and has great components but VERY VERY expensive to run. A recent analysis showed it to be 5x more expensive than running a CR85 which is a good option light and with all the components you might aspire to but a cheaper 2 stroke motor to maintain. Same goes for KX100, RM100, RM85L, YZ85. KX and RM100 are particularly good bikes.

Whilst the smokers are excellent little bikes the power delivery doesn't suit all riders. I run a CR85 and modded DRZ190. The DRZ is quicker for some riders who suit a 4 stroke more and thrive on the more forgiving and hi torque delivery. The weight of the DRZ has low Centre of Gravity and is not so much of an issue once the bike is rolling.

Final thought is that my 15 year old is now getting pretty large for the CR85 and (DRZ) and is looking to move onto KX125 .....

Thanks for your reply Beamishnz.

Yeah it's the crf 150rb I was thinking of.

What's so expensive to run with that particular model ? I can see it being more expensive to run than a 2 stroke , how does it compare to a well set up drz to run ?

I know what you mean about the power delivery with the 2 stroke and that does concern me with my lads ridin style , not sure he's ready for that at the moment.

The yz 85 looks a great bike and weighing only 65 kg would feel so much lighter than a drz 125.

It's that "horses for courses" issue again!

Yeah it's the crf 150rb I was thinking of.

What's so expensive to run with that particular model ? I can see it being more expensive to run than a 2 stroke , how does it compare to a well set up drz to run ?

you are basically maintaining a small bore race bike...

valves, top end, timing chain, and all the other things that need to be maintained on 250's are just as important on the 150...

maintenance is more often, and more expensive than the 125

you are basically maintaining a small bore race bike...

valves, top end, timing chain, and all the other things that need to be maintained on 250's are just as important on the 150...

maintenance is more often, and more expensive than the 125

yeah just number of parts and the cost of them is what makes it so expensive. Eric Goor from Forward Motion has written a good book on mini and midi bikes and he did the math on it from 2 race bikes he was maintaining for customers .. just WAY WAY more expensive than a 2 stroke.

I run (amongst other bikes!) a KX250 and CR85 and a DRZ125 and maintain an RMX250 and another CR85 for a friend. From what I can see so far the modded DRZ190 is the cheapest of them all to run. Even with the 190 it is an understressed low reving engine compared to all the others and whilst it has valves, timing chain and cam that the 2 strokes don't have they are basic cheap parts unlike the hi tech stuff on the 4 stroke full race MX bikes, and no where near as critical on valve timing and shims etc.

The full race 4 strokes are so expensive to maintain that I know guys who buy them new, run them a season and sell them to buy another new one rather than pay for the servicing .. they reckon it is cheaper that way!!

These new generation 4 strokes are going to be worth nothing 5 years down the line because a rebuild will be more than the bike is worth.

Now you understand the enthusiasm for the humble DRZ :busted:

Okay I've taken note of How tunable and cheap to run our drz is .So will start to piece together costs and tuning options.

This is what I am considering thus far :

kx/ rm 100 front end assembly ( would appreciate a model year for the correct front end )

Cr 85 rear shock ( again would need a model year which is compatible )

Frame cradle to stiffen frame.

Engine :

Pro circuit t 4 exhaust seems the popular choice

What to do with the engine upgrades is where I am unsure which direction to go . It would be helpful for advice in this area please .

Do I go for a 144 cc and then realise that I should of done a 190 cc upgrade ?

I want to do this once and try to get it right first time .

Thanks if you can help. :busted:

If you go with the 190. And you intend on trail riding/light motocross use. He wont outgrow the bike (Im saying this as a 5-9 170lb 33 year old who owns and races "full size" race bikes but loves his little drz) When hes done with it, it will make a great dads bike. Weight is a big issue though. I also own a 150rb and as far a performance goes, its pretty tough to beat. but I am also in the understanding that performance comes at a price. If you can do your own motor maintenance, theres nothing to be afraid of. they are just two entirely different breeds of animal. The DRZ is fun cause its not one of those bikes that really gets away from you. With all the mods we do its fast for what it is, a two valved air cooled baby thumper. And maint. is almost non existent. But its pretty hard to go away from a fully equipped race bike that needs nothing but gas right out of the box (150rb). How mechanically inclinded are you? If you read this board, you will realize that most on here like to modify what they have about as much as they like to ride them. Thats alot of fun also if your into that....


Ok you have seen the light! ... but before you start your journey let me tell you that the easiest and most cost effective way to get your son onto a powerful, light bike with good componentry is to buy an '04 onwards CR/KX/RM85 .... and that is great if he is the pin it back, throw caution to the wind sort of rider that is happy to rev the nuts off it, roost 6' high and work out what happens next in a nano second. If however he is the slow into the corner fast out sort .. or the type of kid that wants to be able to back of on a root riddden climb and put the gas back on as he nears the top then a modded DRZ is the perfect weapon and a heap of fun to build and ride.

Now to the specific advice you're after:

Best front end IMHO is RM85 '05 onwards that way you can use the stock front wheel and brakes which are fine for the job. You need the RM85 or CR85 triple clamp to go with it. If you can get the forks from a big wheel model - they have stiffer springs and more aggressive valving which is what you need for the porky drz. You will probably wan to upgrade the fork springs anyway and the best bet there is the BBR CR85/CRF150R springs which fit the RM85 forks too. You can run just one BBR spring and one stock spring if you find the BBR option to firm.

Next you need to look at the shock. I'd be looking '04 onwards for the CR85 shock and just go for as low hours as you can find. See posts on this forum esp DRZSuzook for mods to the shock which are minimal. Again go for BW one which has hgher spring rates. Alternatively hunt down a Works Performance DRZ125 shock. These are very good but expensive.

BBR Cradle is essential and again can be picked up from ebay or direct from BBR. If the bike is to be ridden hard I would strongly recommend a little frame strengthening. This is not difficult or too expensive. DRZSuzook has a few good posts on it and I have picks of a how I did it to be posted soon along with templates for the frame fillets :moon: .... but bit rushed at the moment.

Now this brings us to the engine choice. I don't know anyone who has a 143 kit that wouldn't prefer a 190 kit and know lots who wish they had gone down the 190 route rather than the 143 ... however the 143 is definitely cheaper option. I don't know the exact costs but the 190 kit for cylinder/piston/gaskets/cam/titanium springs is $800. If you went down the 143 Wiseco route. Piston $100, Gaskets $50, x320 megacycles cam $100. Springs $50, Boring of stock sleeve $70 ... so approx $500.

In both instances you will need a pipe ( I like the outlaw pipe from Engines Only) and a carb (26mm for 143 kit; 28mm for 190 kit)

In the total scheme of things the extra $300 for the 190 kit is well worth it IMHO and it arrives all together ready to bolt on with very good back up from Engines Only ... as TWTom says a lot of us like fiddling but the 190 kit makes it pretty simple and once it is up and running there is about as much maintenance as your lawnmower! :p

My 190 kit and other hot bits may become avaialble early next year because the guy I built the bike for has moved overseas ... just a bit reluctant to split it up just now because it runs so well :busted:

Make sure you read the RM100 conversion sticky at the top of the forum ... plenty of good info there.

Thanks Tom and Beamish,

Great replys very good info

I am mechanically minded and will get a lot of satisfaction from building and perfecting this Drz , nearly as much as riding. Will have to learn as well , but that's part of the fun too.

I've just set up a 07 crf 250 x play thing recently for my self and am very pleased with the results.

There's alot more scope with this Drz . The lad will also benefit from riding a stock drz 125 then advancing his riding skills and mechanical skills along the way . So I am convinced this is the ideal way to go.

My Lads more of a conservative rider and will benefit from the smoother power delivery.

Could well be interested in any 190 bits if and when they come up. Drop me a pm or post Beamishnz.

Thanks again

get an 85 or a crf150r the suspention on them is uncomparable to the drz125 and so is the power. modding your drz125 is only going to be a waste of money and its still going to be a drz125 if you want performance go with a race bike the 85's are cheep and are alot better engine and suspention wise. the crf150r/b will be a little bit more expensive but its a four stroke .

You are correct about the suspension on an 85 being better than the drz....thats why if you read the post above you will see that he is intending to switch the suspension to an 85 setup. My DRZ will eat a 85. (granted it has more than the basic mods). You can do anything you want to this fun little bike. Lifes not all bad "still" being a DRZ. As you read above power delivery is a concern. A built DRZ is off the charts as far as the fun factor. I dont think you can really go wrong.


Hello people,

Been of the site for a long time. Just read the post from xgames.

Well we did mod the drz, shipped over a 190 kit , fitted rm suspension and a two brothers pipe to boot. All I can say is it was the best advice I had thanks to members on here. The bike is a hoot to ride great fun. My lad loves it and the bike has so much torque and is easy to ride. My boy is fast becoming as tall as me but as Tom has said you don't out grow the bike.

I will buy and sell bikes but as long as I can haul my butt on the bike and my boy still loves it , it will be one bike we will never sell.:smirk:


I couldnt agree more. you will never outgrow it and never get bored with can you go wrong?


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