Eric? Port. & Polish. Questions

[_j0kA_]

Hi,

Im looking for some more power in my stock, 01' RM 125, and I was considering pipes until someone mentioned to me that porting/polishing an engine will give me more "bang for my buck" then ALL of the aftermarket parts put together..

My questions are:

1) How much does it cost?

2) How long does it take? ( Appx. time for it to return to my house )

3) What are the chances of something 'messing up'?

4) Will I need to rejet after?

5) How much more power will I gain? ( I am 180 pounds, so my 125 is a little on the light "power" side for my weight.. Would it be somewhat equal to a 175-200 cc? )

6) Will people call it a "cheater" bike?

7) What kind of gas will I have to run?? Will 93 pump be okay?

8) Will I have to run oversized rings, pistons, etc..??

9) What are the pro's, and con's of porting and polishing for a local racer that plans to do something with a " racing career "??

10) What other mods/hop up's would you suggest besides porting and polishing? Im thinking more along "bolt on" ( or little tips that will make my bike perform better.. IE: pack the silencer tighter ** just an example ** for more power.. ) type hop up's, but im open for suggestions..


Thanks for your time,

Dan

 

[Durt Cycler]

Eric G. is very busy so I'll try and answer some Q's.

1) Around $120 from Eric plus he gives a discount to DRN members.

2) Eric is REALLY busy with doing alot of motors so check out his website for turnaround time.

3) With a expert like EG probably like zero to none.

4) I'm not too sure but I don't think you will have to.

5) You won't gain anything in displacement but it would be my guess you'll see about a 5-10HP increase with a expert port job! (most aftermarket parts don't even come close to 5HP)

6) A bigbore is a cheater bike I bet most racers out there have there cylinder ported!

7) Beleive it or not but porting actually lower the fuel octane requirement. It is still wise to run 93 pump for safety sake.

8) No. Porting makes the exhaust ports bigger increase the exhaust flow. I'm running a std. plated cylinder with Pro Circuit porting.

9)PROS - The satisfaction of spending your money on a mod that WILL work. CONS - Well I can't even think of one!:confused:

10) Get your jetting dialed in, Carbon fiber reeds! either just the reeds or better yet a reed cage, pipe/silencer combo, if your looking into using race fuel have your head worked/milled for more power, and if your looking to get into a MX career set your suspension (stock sucks).

Hope this helps you if anybody else would like to post and give him some more advice do so! Good luck. DC

 

[Vytas]

I got my cylinder for my 2001 RM250 back from E.G. around January. Just had my first opportunity to ride my bike last weekend. Prior performance was OK, usual Suzuki poor low end that disappeared into hard hitting mid-range. After last season I sent the cylinder in for "Mo-Better" porting, put on a set of V-Force reeds and played with the jetting. Performance now is fantastic. The mid-range hit is gone! The bike starts to pull off the bottom and the power just keeps on coming. The increase in power across the band is great. Aside from the mods mentioned rest of bike is stock. The porting services done by E.G. are probably the best $110 you will ever spend on your bike. I am waiting to get my kids CR80 cylinder back which is having an AMA 0.080 overbore and porting done. Later this year I am sending out my other boys KX65 cylinder out for AMA 0.080 and porting as well. E.G. will continue to get my business as long as he is in business. KUDOS to E.G and Forward Motion.

 

[_j0kA_]

Thanks for the replies!!

Do you know what I am thinking about when I say that 'you will have to run higher octane gas' in order for it to perform right?? It might have been milling the head, but im not sure.. I got a little confused when I got into the topic of porting/polishing..



I have noticed that on my stock, 2001 RM 125, that there is NO HIT at all.. Im sure this is good because it ensures smooth riding, but I want some major "jazz" in it.. Will a port & polish job do the trick??

And "ARE" you positive that I WON'T have to run anything oversized, or non stock?? I told my dad about porting/polishing, and he told me that it would cause you to run oversized rings, bigger piston, etc..

But to tell you the truth, I don't think he knows a lot about bikes.. When I first bought my bike ( Oct. 9 / 01 ), he had NO bike engine experience.. So, basically he only has 6 months "begginer" experience, yet, he can tell me how everything works in a bike?? ( Sure he can have basic experience of a 2 stoke engine, but I believe bikes are a little different.. ) Does this make sense to any of you??


And finally, just to double check.. If I get this done, I will still be able to fix my bike the same as before without having to buy oversized pistons ( rings, etc.. ), or special parts???


Thanks,

Dan

 

[_j0kA_]

At $110 and 4-6 week turnaround, that doesn't sound bad at all!!

Do any of you know anything about sprockets??? I am getting a new chain, countershaft, and rear sprocket.. I figured that from everything that everyone has told me, that I should go up one tooth ( 50 ) on the rear for a little more bottom, with around the same top.. But my dad figured from talking to all of his "friends" that I should go up two.. I told him that I wan't to have around the same top end because I like to rev my bike, but have a little more bottom.. I don't really see how a 51 will work outdoors, but then again I have never changed to a different sprocket size before... I don't know how drastic the change is, so could someone fill me in?


Thanks a lot,

Dan

 

[bruce j]

Porting a cylinder will definitely NOT create a need for oversize rings or piston. You might have to re-jet, but Eric can help you with that. Bolt-on parts ususally require you to re-jet as well. Yes, porting will give more "jazz".

Adding one tooth to the rear sprocket will make a small but very noticeable gain in low-end. It will cut your top speed a bit. Two teeth will make a bigger change in both. It might be a good idea to do whatever other mods you decide on first before you fine tune the gearing, you might find out you have plenty of low-end with stock gearing.

Milling the head can cause a need for higher octane fuel, but not always.

It sounds like your Dad is a great guy, staying involved with your activities and all, but I think he is a little confused about what exactly is done when an engine is ported. Good luck with your career!

 

[spy-yamaha]

Dude- You can port a cylender and still be able to race a 125 in the 125 class right? Or a 250 ported in the 250 class. I thought porting just made for hp not more cc's. Can someone please fill me in here?

 

[bruce j]

Porting doesn't change the cc's of the bike. It would still be legal for 125 class competition. It probably wouldn't be legal for 'stock' class competition, if there is such a thing in your area, though. It would have to run in 'modified'.

Keep in mind that $110 U.S. is a lot more than $110 Canadian. You shouldn't have to pay import duties for service work, but you might have to pay GST.
It's still cheaper than a pipe.

bruce

 

[whyz]

What is a AMA 0.080 overbore from an 80?? Tommorrow i'll be sending in my sons motorCR80 (basic rebuild)and have it bored bigger. I'd like get it to be a 100.. Talked to EG and he said yeah send it in..And when i do this should I have to have the carb modified too for the bigger bore?Thats what i forgot to ask him too.
Thanks...

 

[_j0kA_]

Thanks for the replies!!!

bruce j: Thanks for clearing that up, it makes sense now..
I understand what you mean about my gearing, but my sprockets are due for a change anyway ( 6 months of racing every weekend :scream: ! ).. I can always switch back to stock when I need to change them again.. I don't think that I will be getting any "expensive" bolt-ons yet, so I have some room for trial and error before anything will be concrete..

$110 American converted to Canadian is $173.69.. A pipe cost ( appx. ) $450, so I would be getting one hell of a deal..



Would a 50 tooth rear sprocket be what I am in the market for?? I like my top end, but my bottom is a little weak.. One tooth up, will give me a bit more bottom, with a little less off top.. Two teeth up, will give me A LOT more bottom, and A LOT less top, right??

Im just trying to make sure I am doing the right thing.. Im positive that after I get my new sprocket, I will know if I made the right decision or not..



Thanks!

Dan

 

[bruce j]

Sounds like you've got the right idea on the gearing. The best thing would be to try both and see which one you like best. Lots of racers will run different gearing at different tracks, sometimes even at the same track if conditions are different (like if it's really muddy).

When you ride the bike with stock gearing, do you ever find you are revved out in top gear, looking for more speed? If this happens a lot, I wouldn't lower the gearing. If it does happen, but only once in a while, adding 1 tooth should be O.K. If it never happens, I would add 2. Hope this helps.

bruce

 

[Vytas]

Whyz,
The displacement on the CR80 right now is at 83cc. With the allowable 0.080" overbore the displacement will now be 90cc. This configuration can still be run in the 80cc class. If you go with the Big Bore kit then the bike would have to be raced in the modified class, 80-100?. I do not remember off hand the exact class.

Volume(cc) = ((Bore(mm)*0.5)^2*pi*Stroke(mm))/1000

So in stock configuration the CR80 has a bore and stroke of 47x47.8 using these number in the above equation yields a displacment of 82.9cc. By adding 2.03mm(0.080") to the bore you can deterimne the new displacement.

 

[whyz]

Thank You Vytas...:)

 

[whyz]

one more question

What will your sons kx 65 become?? an 80cc?
I was trying to do the math but not very good at it.

and would I have to get new pipes for the bigger bore?

and if you.....(oops thats 2 question going on 3):confused:

And good luck on your mods JOKA and your racing too....

Sorry I forgot to put it in the mini forum..:mad:

 

[Vytas]

The exact number would be a 71cc motor. But there may be rounding error involved. So figure that it would be right around 70cc. A 250 with 0.080" over becomes a 265cc. I think that this will be the next mod for my RM later this year. Finsihed putting together the CR90 together this weekend. Kid rode it and said big improvement, more torque and has a beefier sound. Good luck to all.