Suzuki rm 125 porting

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5/30/2019 10:44 AM

just want some opinions on my cylinder i bought this bike a while ago and told it was ported im not a 100% what im looking at
it does look like its had some grinding done so i thought i would get some pics while i ts apart see what anyone thinks







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5/30/2019 10:47 AM




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5/30/2019 1:35 PM

Yes it has had some work done to it..........

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5/30/2019 1:44 PM
Edited Date/Time: 5/31/2019 12:19 AM

thanks for the confirmation nice to know i didnt get miss sold

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5/30/2019 5:46 PM

Ouch that looks rough...

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5/30/2019 6:47 PM

Paging Brody!!!

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5/31/2019 12:16 AM

slipdog wrote:

Ouch that looks rough...

does it not look like its a very good job then the pictures aren't the best the lighting makes it look a bit patchy

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6/4/2019 12:39 AM

bumping this back up would still like a bit of feedback if its a good or bad job and the reason why

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6/4/2019 12:54 AM

dazza2 wrote:

bumping this back up would still like a bit of feedback if its a good or bad job and the reason why

It’s not a very clean/ uniform porting job (have seen way worse), but it could stand some correction... it looks like whoever ported its goal was to just take off the casting imperfections in it; and there appears to be a lot of chatter from the bit used... that being said it’s still usable as it looks like it wasn’t ground on much so I believe it can be cleaned up...

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6/4/2019 1:55 AM

thanks for the info thats the sort of feedback i was looking for
had me a bit concerned when it got called rough as long as it useable ill leave it as is for now maybe send to someone in the future
Thanks

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6/7/2019 8:34 AM

Measure from the top of the cylinder to the top of the exhaust port. I think stock would be about 29mm down and a common practice is to raise the port to 28mm. I'm just curious if that was done.

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6/7/2019 8:51 AM

Most notable porting changes usually start in raising or lowering ports two strokes. Like Ryan said above a quick check of exhaust port height will help to see if it was a clean up or actual porting

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6/7/2019 9:10 AM

Raising port heights will gain you hp, and peak torque numbers, matching cases will bring low end performance up as the engine can flow more easily at lower rpm if the transition between the cases and the transfer ports and rear boost port are matched perfectly. And ridges or mismatches between the two will
Cause poor flow characteristics till the engine can flow enough fuel and air to negate the obstruction of flow, most stock port heights are aggressive enough for mortals, if you want to make more power all over, smooth out every single transition you can so there is nothing that can impeed airflow, ports don't impeed air flow, mismatches in the cases and casting flaws do

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6/8/2019 9:47 AM

thanks for all the relplys i will check on monday with the calipers and see if it has been raised or not
do you know what sort of effect raising the exhaust port will have where does it move the power too any info would be appreciated

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6/8/2019 1:30 PM

Raising port heights up wil increase peak hp and peak torque numbers, but also move those peak numbers higher in the rpm range, but may start to hinder low end performance if taken past a certain degree, and rm125's in my opinion, haven't ever struggled to revv, What year of rm125 is it?

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6/9/2019 10:38 AM

its 08 same as 07 it definitely seemed like a more top end motor last time i rode it especially compared to my 98 kx 125 which is the polar opposite to the rm
ill measure the exhaust port height tomorrow

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6/10/2019 2:45 PM

I've measured the exhaust port height with the calipers it wasnt as easy as i had hoped i used the step measurement and done it a few times it came out about 28. some low digit it wasnt the most accurate
i also tried it with a tape measure and got about 28

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6/11/2019 9:42 AM

so i re measured it and i think its more like 27

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6/11/2019 9:43 AM
Edited Date/Time: 6/11/2019 9:49 AM

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6/11/2019 9:44 AM
Edited Date/Time: 6/11/2019 9:49 AM

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6/11/2019 9:46 AM
Edited Date/Time: 6/11/2019 9:50 AM

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6/11/2019 9:48 AM
Edited Date/Time: 6/11/2019 9:49 AM

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6/11/2019 12:22 PM
Edited Date/Time: 6/11/2019 12:24 PM

27 or 28 are both pretty high and I would assume it's been raised. As you say above, it's a revver compared to your 1998 kx125.

You don't have any good pics of the roof and powervalve of the exhaust port. Does it look to be milled/sanded? That will give you a good indication too.

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6/11/2019 2:33 PM

power valves out at the moment not a 100% sure if its had any work though

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6/17/2019 4:30 AM
Edited Date/Time: 6/17/2019 4:31 AM

Get a degree wheel and time out your port duration's the right way. Find out at what degrees the ports are opening and closing and the total blow down, you can much more accurately understand whats happening within the motor and work with a good tuner from there. 2 strokes are way more complicated then most people will ever understand even though there are no moving parts besides the piston to control timing and the port windows themselves. Sometimes the duration numbers that should work on paper and calculations don't translate into a better running bike and i believe most great running 2 strokes are built by trial and error. Setting up the power band to suit your riding style is also important. A 125 with no low end and all top is hard to ride for normal guys and the RM doesn't have much low end to begin with. If your exhaust port is now 2mm higher then stock you probably now have less low end then a stock bike.

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6/17/2019 5:28 AM

hi thanks for the reply i will look into that
its not too bad to ride but compared to the kx its completely different
my measurements may not be the most acurate i probably wont dig too deep into whats been done this time around just want to get it up and running now

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6/17/2019 7:21 PM

I have to agree, rm125's haven't ever really
Been notorious for bottom end delivery, I will say my 99 was an acception, I bet that engine would blow the doors off a new yz125, it was impressive, it had a way better mapping setup though, pwk longbody, with a powerjet, it was a sweeet powerband, and the pro circuit exhaust was explosive, bottom to top, it pulled effortlessly, I owned that one recently, and when I was 16 I owned a 2000 rm125, and i can for sure remember it had zero low end, allllll top, and the pc exhaust was the same for it as well, explosive, such a good setup.

Now for your engine, I can't say for sure, but judging by the looks of what's been done, it's merely been a port clean, and possible matching the cylinder to the cases, just by looking at the degree of grinding, and blending that's been done, there hasn't been any port height alterations that I can see. If you get a couple sets of chop sticks, you can wrap any grit of emery cloth (sand paper) you want around it, 80-120 grit works good, and then just sand it out by hand without buying a dremel, may take longer but it still
Achieves the same results, and it will get into the little corners of the port sides easily. I use this method to finish all my cylinders by hand after any dremel work, just seems to come out more consistent and cleaner, Iv gotten a few cylinders back from porting work that's been done, and ended up finishing them by hand, to smooth out the quick work that had been done. All in all though, nothing bad has been done, old school method was knife edge the port bridge, but it's been proven that a rounded surface is better for splitting passing air, so everything looks like it's at a great starting point if you want to experiment and smooth out your porting surfaces. If I get onto porting my 125 sx cylinder in the next bit I'll post some before/after pictures too, I don't alter port heights myself, mainly due to the fact I don't have a 90 degree dremel head small enough, but I usually find you can uncork a lot of airflow just by smoothing everything out

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6/18/2019 12:10 AM

thanks for the reply im going to get it all back together this time around then maybe next time try and find someone to send it to
i did email a company here in the uk but they didn't seem keen as someone else has done work to it which is fair enough i suppose

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6/19/2019 5:42 PM

dazza2 wrote:

thanks for the reply im going to get it all back together this time around then maybe next time try and find someone to send it to
i did email a company here in the uk but they didn't seem keen as someone else has done work to it which is fair enough i suppose

Try Justin at Gibbs performance in Devon! He ported my rm 125 and she rips! Just shy of 40hp at the wheel

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6/20/2019 7:35 AM

dazza2 wrote:

thanks for the reply im going to get it all back together this time around then maybe next time try and find someone to send it to
i did email a company here in the uk but they didn't seem keen as someone else has done work to it which is fair enough i suppose

psr racing wrote:

Try Justin at Gibbs performance in Devon! He ported my rm 125 and she rips! Just shy of 40hp at the wheel

What sort of cost roughly are you looking at for a port job by Gibbs??

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