01 CR125 Squish

[usgpru27]

What is a good middle of the road squish setting for a stock motor? My manual doesnt even address it at all.. Do they make differant base gaskets to adjust? On our roadrace 2 strokes squish is critical. Seems on these dirt bikes not so much.. Any insite appriciated. Thanks

 

[marcusgunby]

They can be a s wide a 1.4mm and as narrow as 1mm-std is about 1.2mm i think.If you run good fuel you can go down to 1mm.You can buy different gaskets from cometic.Honda doesnt sell them, only ktm setup the deck height etc with different gaskets.

 

[usgpru27]

WOW that is huge.. Our roadrace bikes run .63 - .68mm. Is the recomended deck height 0 and the squish determined in the head profile? I will be getting a VHM or Phat head with custom inserts. Hope that 0 deck is what the standard is since it helps with profile choice. Thanks marcus...

 

[marcusgunby]

I cant remember if the deck height is 0-i think it is.Dont forget in mx we tend to run old parts in the engines -ive heard road racers put in new cranks on a regular basis?? well most mx bikes get a crank only when it seizes-so i think thats why the bigger squish?

 

[usgpru27]

Old Parts... Man I need to change my mentality. You are correct.. On our Roadrace bikes we change pistons every 250miles or 3 hours. Cranks are replaced at 1000 miles or about 12 hours. Along with this every clip, bearing and seal are also replaced. Cranks are balanced and the entire engine is bluprinted to some VERY close tolerances. Typical rebuild is about $1500.00 But since we are getting close to 42hp from a 125 motor that may explain a lot. And we run them 9000 - 13500 when they are running.

It is my understanding that the 01 CR cylinder has the same port configuration and port timing as our teams RS 250. I have a lot of experiance with this and plan on changing some of my CR stuff to get the delivery I am looking for..

This is great stuff... 1 mm squish.. Wait till I call my engine builder.. !

 

[marcusgunby]

When i say old parts i dont mean secondhand, just that most dont replace cranks at regular intervals.On a 125 i replace the rings every 6 hours and pistons every 12.

Yes the cr does share port timing similar to a RS and thats one reason why it has little bottom end power, the 05 cr125 has a similar setup but uses a better pv setup(much closer to the piston) and gets much better bottom end.The 01 wasnt a good mx engine at all and cant really be modified to run like a YZ or ktm.Mine had 36hp at the rear wheel and was fast but not easy to ride.

 

[usgpru27]

Your comments are consistant with what I have found.. What did you try to get what you wanted.. With a fresh crank I am thinking of getting the squish down to .8 - .9 and bringing the head volume down to say 7.0cc and if the timing is adjustable give it .2mm more. Is it overheating that you need to watch? I will also be using Higher octane unleaded like VP.. They are one of my sponcors so.. Very interested in how far you can push the tuning without loosing the reliability. With exception of the pipe (not sure how effieciant they are) I dont see why 40hp should be a problem with a controled powerband..

Any thoughts?

 

[marcusgunby]

LOL your dreaming of a mx engine with 40hp that lives for more than one ride-dont take this comment wrong its just you have to give up alot of peak hp to get some bottom end.The factory KTMs dont have 40hp at the rear wheel and they have a way better base engine to start from.

Our main problem was detonation-in the UK we dont have exotic fuels so we are limited what we can use.

I tried lowering the cylinder-closing up the squish/v force /pipes and silencers/big carbs -ignitions etc.Basically everything i could use-and a std YZ engine was faster on a mx track.Sorry to tell you this but the 01 cr125 is one of the worst engines for mx-its based on the RS and i think thats where its problems lie.

Anyway the basic thing im trying to say is dont go chasing big hp numbers as this engine just looses any bottom end it has, and you need it to get round a mx track.

heres the best dyno run from the cr engine-note however this one is a eric gorr 133 kit and it still doesnt have enough bottom end power.

http://dirtrider.net/forums3/showthread.php?t=97637

the other one is 01 cr125 compared to a 05-its the pv thats the problem on the 01 and i dont see a easy way to fix it.

 

[usgpru27]

Marcus, No worries my man... This is a great topic.. I will have to see what the deal is.. Actually my comments re: the HP are just a referance. On the RS we have MANY MANY set ups. Since we run everything from very tight 1.8 mile ones all the way to Daytona we have many set ups. I agree that the goal here is to get the bottom end strong and also rideable.. No wonder I got this 01 so cheap... LOL.. But I am a beginer on these and it shouldnt be that much of an issue for a little bit. I think the best thing to do is talk to Eric at this point.. It is my experiance that making the correct adjustments to timing, squish, head volume, jetting as a package and not individually usually creates a good rideable package.

On the RS125 I have a Daytona set up that yields 43HP with no bottom end below 10,000. That is OK because all I need is HP.. My Talledega set up only yeilds 38.8HP and falls flat on its face at 11,500. But it also has 6 more at 9,000 over the Daytona set up. Issues with ridability are addressed with jetting and timing for the most part. When I first did the low end set up I had a lot of issues with the hit. the RS125 doesnt have a PV. We richened up the Power Jet and it smoothed it out quite a bit..

This is all good stuff. Thanks for all the information. Ultimatly to me a good smooth running engine that has great ridability is the key.. Thanks this is a great exchange..

 

[marcusgunby]

With a mx engine you want it to peak at 11K(35hp) and to have 15hp at 7K-if you get that you have as good as most 125s do.

I think the 02 cylinder fits and i got a much better spread of power(34.5hp peak)a big bore 133 is the way to go really for punch per pound.

 

[usgpru27]

While I think I will want to keep the bore square for now i will look into the 02 cylinder. I would think that Honda would have made the appropriate updates after 2 years of negitive results. Thanks for all your information. I have a note out to Eric on his forum asking the best combination and all the parts he would like me to get (outside the standard Honda parts) for a complete rebuild.

Appreciate your knowledge.

Bill

 

[Milhaus]

Hi. Would you mind updating us with your results, Bill?
I also recently got an 01 CR250R for a great price, and am wondering what can be done to improve it (albeit on a bit more of a budget than I think you're working with : ) ). I could have gotten a 99 YZF400 for about the same price...wondering if I made a mistake.

 

[usgpru27]

Well it has been around zero degrees so it is on hold. I am not really sure what I am going to do. I am thinking it is best to start with some mild changes first.. Taller piston and head..smaller leaded head volume.. to see how it reacts.. Tighten up the squish a touch... and add some timing as I will be running leaded C-12. I would think that this should do what I am looking for.. And I have a 125 not a 250.. Since I totally crashed my bike in the driveway this weekend.. I think a 250 may be to much.. :bang:

 

[Mike R.]

How you wreck it in the driveway?

Not being a smart@ss, just curious?
Did it damage the bike? Or you?

 

[usgpru27]

You know I am really a dam dork. :laugh: . Since getting the bike I bought a Bills Pipe and new bodywork, levers, grips ect.. I worked on it in the garage as it was over freezing this weekend. I say to myself.. Warm it up and take it for a spin.. This is my first dirtbike and I have only ridden it in the driveway and only once when I got it. The driveway has about a 6 inches of snow with only some wide tire tracks down the lenght. I get down to the street and turn around.. Heading back I crack it and hit second.. Thing heads for the berm from the tracks and totally washes out and I do the big face plant.. My left knee slams into the frame and I can barely get up.. I then see my wife on the deck :eek: Real funny.. First is to check the bike.. Nothing but a bent brake lever.. I get it to the garage and park it. Deal is I shattered my kneecap in 2000 on my roadrace bike and it has 4 pins, 3 screws, plate and some wire. I pull my pants down in the garage to see if the screws pooped threw the skin.. Almost.. Back to the deck... Wife ... :nener: Now it is KILLING ME! I am used to this stuff and glad I didn't hurt it more.. BUT WHAT A DAM DORK!! It is the lesson I needed. I have ALL the gear and some Serious knee protection.. From now on it doesn't go into gear unless I am in my gear.. More than you wanted to know but I feel better coming clean on my total bone head move!!

 

[viking20]

Glad to hear you didnt do to much damage to yourself , LOL
We had a cr 125 from -01 as well. My son is a pretty fast kid , and the cr could certainly use a bit more bottom end. We , like many others copied some of the tricks that Marcus and Steve125 found worked best,V-force , Vertex piston without the window , different pipe etc.
What worked in the end was getting a 133 cylinder from Eric , ported for bottom/mid.The kid still had to work really hard , but it was much better.
We now have a KTM 125 , a lot more power , but a lot more work is needed with the suspension now......

 

[marcusgunby]

You know i have forgotton most of the tips for the 01 cr125-there was so many LOL, and overall they had such little effect:(

 

[usgpru27]

In the end it is all relative to rider ability to which I have none. Still amazes me that a guy that is top 5 in the National 125 scene can wreck in the driveway.. It will be fun to figure this CR out.. Thanks for the tips..

 

[Mike R.]

Glad you came out ok!

Sound like no fun especially with your prior kneee problems.
I am still amazed though how many people always say the 00-01 CR has not bottom end.
Granted it might not have what the YZ or others have but, unless your a serious racer its a great bike.
I have owned numerous 125s and granted it might not be the quickest down low it still has plenty of rip to it.
Seems only in 05 has Honda really developed an all around good 125 with some bottom motor but, from 98-04 they where still good.
My last MX bike was an 04 KX125 and it had some bottom but as far as supsension and just about everything else I would still take an 01 CR.
You just take everything MX mags say seriously half the time.

 

[Robin13]

My cr125 has a 1.25mm squish and runs well, next time I'll try a 0.010" base gasket (0.020 is stock) to get a 1.00mm squish wich is supposedly good for shifting the powerband down the rpm range.

 

[usgpru27]

Robin, You are going in the same direction that I want to. On our roadrace 125 we run .67 squish. I know that there are limits with every set up but I will be running leaded C-12 for Det. protection. Being that high octane leaded burns slower I will also be putting in 2 deg of timing to compensate and another 2 for some bottom end punch..

Let me know how the 1.0mm squish works for you. This was the target I was looking at but was going to set at 1.1 - 1.15 with the other changes and work it down. This along with playing with some head profiles and band width. I will be using a VHM head since the inserts are only $20.00

Odd thing is that this bike is more than I will ever need but like doing this development.

 

[Robin13]

Odd thing is that this bike is more than I will ever need but like doing this development.

Same goes for me. I'm not as educated on engines as you are, but I like to adjust and try things out. Last week I took my fork apart with a friend who helped me. Next time I take the topend off I'll try the basegasket thing. By the way I run 98 pumpfeul (95 is normal in holland) so I don't think pinging will be a problem.

 

[usgpru27]

Robin, You are in good shape.. I mean these things are supposed to me fun right. What is nice about these engines is they seem to be bulletproof. My Yamaha TZ roadrace motor is going back out to California for another $1,000 rebuild as the crank bearings have some play after 2 hours of riding.

I believe that fuel is expensive in Holland correct? I am running the VP 108 octane C-12 because I have a lot of it. We use it for our roadrace bikes. It is only about $3.00 a gallon for me so why not. Premium pump unleaded 98 octane is $2.15. It is more of an insurance policy than anything else..

Let me know how you make out with the top end.. May take mine off this weekend also just to check inside..!!

 

[viking20]

Gas costs about the same all over Europe , give or take...
With the current value of the US$ , I can buy 2 LITERS of pump fuel , every time you buy a gallon of the fast gas.. :ugg:

 

[viking20]

Oh yeah , and BTW , one liter of any race gas will cost me about 5 $.... :ugg: :ugg: :ugg: