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Eric Gorr 2005 Yz144

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In the topic "thinking about boring out my 125" a lot of information was exchanged reguarding overboring a yz125. I had mine done by Eric Gorr of Forward Motion, and I figured I would right short review.

Bike History - I bought the bike during the fall 2006 and put about 3 or 4 short rides on it bringing the total hour to around 5. I installed a uni filter, hand guard, a skid plate, and a v-force3 before rthe last ride. I planed on the 144 before I got the bike, but thought I would do it during the first rebuild. But, having the inability to keep anything I own stock, I sent the engine out a few days before the new year.

Choosing the engine builder - I shopped around before I chose Eric Gorr. I contacted Moto814, Eric Gorr, and a few others that are not as well known. I also looked into the Athena kit. Eric Gorr was the least expensive, and the next least expensive was moto814. I chose to go with Eric after speaking with him and concitering price. The descision was not made on price alone. Speaking with him certainly instilled also of confidence. He asked me questions about what I was looking for and did not just answer the questions that I had. I chose to have Eric port my engine for overall gains. I did not want a top-end screamer with no low end or the opposite. I was looking for more gains everywhere with a concentration of improving the low-mid range without loosing ANY top end. I did want gains in the top and certainly didn't want to loose anything. Eric listened to my requests and explained the porting and recomended running the higher compression head if I had race fuel available - I do. I did chose to run the higher compression head and the job out take a few weeks.

Sending the engine out. Removeing the engine is very simple. Once it is out, it is unbelieveable what a 125cc engine weighs - or doesn't weight. I put the engine in cardboard box just slightly bigger than the engine. I put extra cardboard on the bottom and pack bubble rap and towels all around the engine. Once packaged, the box weighed less than 60lbs and cost around $30 to ship from Pittsburgh with $1000 insurance - too much I know. I called Eric a few times and sent a couple of e-mails to make sure he had received the engine. I did not receive any return e-mails, but did get in touch with him on the phone. The engine arived fine with no damage. I called about a week later with some other questions (pipe, silencer, ect.) and he said things were ahead of schedule, but the engine a little over 3 weeks later. Not early but certainly not late either. Turn around time was what he claimed. The engine came back in the same box I sent it in packed well with no damage, and all holes (intake, plug, ect,) were taped up just as I had do when I sent it. Once I got the engine back, I removed the head to see what I could see. Suprise, a bigger piston, cut power valves, and port with material removed. Looked fine to me, but what do I know? Total cost including shipping was $530 including shipping. That included everything - piston, porting. head mods, case cutting, shipping, ect. Also, when Eric Gorr goes your engine, he includes one of his books for free. I chose his Performance Handbook, but it didn't come with my engine. I called him and I got the book a few days later free of charge. It is an outstanding book and I would recomend it to anyone that rides bike and can read. Topics from what to look for when buying a used bike, to port timing. It is simply excelent.

Engine install and set-up. Reinstalling the engine is almost as easy as taking it out, but takes more time. I used a torque wrench on everything (even my valve stem caps), and lube the rear suspension linkage and swingarm so it took some time. Once I got everything back to gether, I poured in some Gearsaver, and coolanol. After some suggestions from Eric Gorr and some great people on here, I chose to run the following jetting. Main 450 - needle stock 5th clip, and A.S. 1 turn out. Stock is a 410, 4th clip, and 2turns out. I ordered more pilots, mains, and the 2007 needle, but the run in was done with the jetting I stated before. Keep in mind it is 32 degrees, and i wanted it rich for break in. I also chose to run the FMF fatty (not the factory.) I called FMF, and they confirmed that the Factory Fatty, and the Fatty are the same bend and only have a different coating. They also stated that the factory fatty has proven to make around a 1/2 HP more than the Fatty do to the way the sound waves reflect off of the metal itself. I will give up 1/2hp just so I don't have to look at a rusty pipe. I am also running a v-force3, and a FMF turbinecore 2. I am running Sunoco leaded 110 octane (strait for now, but will try 50/50) mixed a 32:1 with motul 800. Once I got everything together and gased up, it was time for the heat cycles. Yes, I was very excited - Very, very excited. I turned on the fuel. I have to admit I was shaking. It fired up on the 4-5 kick. I stumbled to get to the choke so the engine didn't rev. I kept the rpm's very low while the bike warmed up. I varied the rpm's just so it wouldn't foul becuase it was rich - very rich. It smoked like crazy and wasn't crisp although it never fouled. I let it warm up until the tops of the rads were warm, the head was warm, and the pipe was hot - about 4-5 mins. I did this 3 times. During this time I noticed a growling sound that sounded like it was coming from the left side of the engine that would go away when the clutch lever was pulled in. I pulled the clutch off (hub, plates, everything) and found nothing. After some research on TT I concluded it is normal an that my close attension to the new engine was the only reason I heard it. As far as other sounds, the piston is a bit louder which is probally do to forged wiseco piston. The FMF fatty and turbinecore 2 have the same noise output as stock if not less. After the heat cycles, I went for a easy 20 minute ride in the wood about my home. Keep in mind that I did no jetting and the bike is running rich even at 32 deg. out side. Could I notice a difference. ABSOLUTELY!!!! Being the first very short ride and still breaking in, I never got above 3/4 throttle or high rpm's. The low end was improved with a smooth transition to a greatly improved mid-range. I really have yet to get in to the higher rpms, but it pulls. The "hit" was reduced but is still there (and I want it to be - hence the reason I ride a 2stoke). I think that the powerband hit seems to be reduce do to the increase in the low and mid range, rather than a decrease in any power. 2 Gear slow wheelies were much easier. I didn't need to rev it nearly as much. I could easily pump the forks, give it 1/2 throttle, and loft the front end. The only hill climb were my short ride was, is about 150 long and around 40-45 degrees but very very smooth. There are no ruts or obsticles, but traction is fair. Stock, I would take the hill in 2nd almost wide open, or 3rd fanning the clutch. I could probally take the hill in 4th with enought speed but never felt the need too (I hope you get the idea of the hill I am trying to explain.) Now I can take the hill in 3rd at any rpm (within reason) without fanning the clutch at all. I actually rode the hill 4 time just to make sure I knew what gear i was in. In 3rd on the hill, I could slow down, speed up, and bring the front wheel up without the clutch. Wow - at this point I am impressed especially because I know the needle is rich. I have a lot of tuning to do. In the tight woods every gear pulls harder, and the clutch is not needed nearly as much. Is the clutch needed? Yes! It is a 144 not a 500. I will say that I think first gear is now useless. I am now running the stock gearing of 13/48. I have a 50tooth rear, and may try a 14 tooth counter putting it at 14/50. At this point I would say that this is simply the best "bang for the buck" I have have ever spent on a bike - and I have spent a lot of bucks. This bike replaced my 2003 yz250f that I like very very much. It does not have the lowend feeling the 250f had, but the lowend and mid range of the 144 is significant and very useful. When I 1st bought my 125, I thought I had made a mistake coming off the 250f. Stock the bike was much, much lighter in the woods and on the track. It handled better that the 250f, but I missed the power. Now that I have the 144(that is not yet jetted properly) I couldn't be happier(unless yamaha comes out with a 160lbs 250cc 2stroke.) I will continue this review once I get the bike jetted and have more time on it. If you have any questions or things to add, please speak up.

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Your Jetting sounds alittle bit rich which could cause your lack of snap your missing cause I feel like mine hits harder then it used to but I have the mid/top porting though. I didn't touch my needle I left it in the 3rd position just went up two on the pilot and a 460 main. Try ridding it again and see if you notice if 1st n 2nd gear wheel spins up to fast mine was doing that at like not even half throttle when I rode it it was like 1 right away 2nd then really fast 3rd so it was like bang bang bang. The 14T front will give you back the rev's in each gear I still can pull snap wheelie's in 1st from near dead idle with 14/48 gearing. I've tried 14/49 and it was alittle snappier was working food for tight indoor tracks I was hitting in the winter around here.

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WAMXP1MP,

The gearing is exactly like you described. I am going to get the 14 front and then experiment with the 48 and 50 rears that I have. Are you running a 45 pilot and 460 main with the needle in the 3 groove? If so, what are temps like and at what altitude? I only adjusted the airscrew and it seamed very rich in the first 1/2 of the throttle. It is probally due to the needle on the 5th groove. Like I said, I have a lot of tuning to do. Thank you for all of the help you have given me.

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I have a 50 pilot at least in it right now 40 was stock it's been awhile since I've dug into the carb then 4 more on the main over stock was 420 I know it's a 460 in it now. Needle is stock in the 3rd clip position air screw was adjusted to 1.5 turns out.

Where I ride it's typically 3000 n under most of the time alittle above sea level unless I goto the cascades. This is Washington so weather is all over the place in the winter in the summer and it was 95 out it still ran awesome. In fact it might be just a tad bit rich mixing it at 40:1. I have the V3 installed and the factory fatty with a shorty sometimes an FMF Q.

Go buy a 14T front it's the same sprocket as a YZ 250F.

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still waiting for my motor to come back. there was an issue where my powervalve arm got bent at e.gorr's so he ordered a new one for replacement. I have been waiting for about 2 weeks on the powervalve arm.

sounds exciting and can't wait to get my motor back.

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I forgot to mension that the stock compression after breakin was 165 and now it is 190 after breaking. You can definetly feel it in the kick starter.

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got word back motor going out tomorrow! yeehaw! it should be hear tuesday next week.

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Hey Airboy808,

How is the weather over there. It is a blistering 8 degrees hear. Make sure you jet it right. Eric Gorr told me to go up one on everything (pilot, needle, main) but I went up way more than just one, although it is very rich now. Just be careful because seizing the engine over a $3 jet would be heart breaking.

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There is so much interest in this 144 mod. I am thinking of doing the same thing, as I have spoken with Eric a few times and am impressed with what I heard. Get that YZ sorted out andkeep us updated.

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There is so much interest in this 144 mod. I am thinking of doing the same thing, as I have spoken with Eric a few times and am impressed with what I heard. Get that YZ sorted out andkeep us updated.

i 2nd! kindly keep us posted mr burgunder! :applause:

one question though, why hasn't eric gorr optimized your bike's jetting after doing all the mods? :lol:

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eric has said that 2-stroke jetting is so different due to all the conditions in which you are riding. just spoke to eric and he said when I get my motor to just try and ride and then jet it.

he mentioned that the 144cc cynlinder is coated to be like it is already broken in so you really do not need to do the heat cycles on the stand. he said to run the bike and just ride it without getting on full throttle in top gear.

he also mentioned a unique way to do jetting is to try running a hotter plug which would be like richening it. (I need to double check this statement). but it sounds a interesting way to quickly test.

my motor should be here by next week tuesday and will have it all back together by the end of the week.

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burgunder: Where did you get the break-in procedure from? Eric or another source? Also did you specify to Eric that you would be using race-gas or pump gas? I specified pump gas.

I thinking of doing 30:1 or 32:1 with pump gas and yamalube. I am basically hoping everything breaks in nice and smooth. My last 125cc two stroke experience was a shifter kart and a kx125 motor which seized down the front straight of the track. So really do not want to do a repeat.

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I have heard you could ran the pump gas head mod's on stock jetting but I sure wouldn't bet on that one. Trust me I speak for experience with my eric gorr 144 but I had race gas head mod's I was told ya just run stock settings from someone I thought was much more educated in the ways of bikes had an '05 eric gorr yz 144 modded the same way as mine.

It siezed in 40 mins of light ridding barely gettong on the pipe, the reason to lean of jetting which in turned caused a lack of lubrication spend the few dollars on some richer jets. Foul out a plug instead!! I doubt you can ship your top end back in 2 days and get it back by friday in HI. Thankfully eric fix mine for free but trust me those jets where richened the next time before it even ran.

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WAMXP1MP : Any advice on what kind of jetting for 80-90 degree weather at 500ft above sea level and about 55%-70% Humidity? I am running a V3, 144cc kit with low-mid porting, and FMF factory fatty/turbine2 exhaust. What is your jetting set-up since rebuilding your top-end?

I just ordered the 07 needle and will be getting some jets. I will get some different spark plugs also.

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WAMXP1MP : Any advice on what kind of jetting for 80-90 degree weather at 500ft above sea level and about 55%-70% Humidity? I am running a V3, 144cc kit with low-mid porting, and FMF factory fatty/turbine2 exhaust. What is your jetting set-up since rebuilding your top-end?

I just ordered the 07 needle and will be getting some jets. I will get some different spark plugs also.

Your just messin with us up here aren't you. :applause:

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have to experiment alittle bit I run #50 pilot #460 main stock needle in the 3rd clip 1.5 turns out on the air screw and it runs good. That should be a safe starting base line.

maybe these pictures in my photo album might motivate ya some.

http://photos.yahoo.com/joe_becher69

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WAMXP1MP : Any advice on what kind of jetting for 80-90 degree weather at 500ft above sea level and about 55%-70% Humidity? I am running a V3, 144cc kit with low-mid porting, and FMF factory fatty/turbine2 exhaust. What is your jetting set-up since rebuilding your top-end?

I just ordered the 07 needle and will be getting some jets. I will get some different spark plugs also.

There is a very good sticky at the top of the page about jetting. Read Chokeys jetting guide. That should explain some things on how to jet your bike to run the best it can. No one can tell you exactly how to jet your bike. Just take the time and mess around with it.

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he also mentioned a unique way to do jetting is to try running a hotter plug which would be like richening it. (I need to double check this statement). but it sounds a interesting way to quickly test.

That is simply a band-aid for rich jetting. A hotter plug makes it run leaner by the way. But when you run hotter plugs you start messing with the pistons crown temps which is opening up a whole new can of worms.

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I got my break-in procedure from many different sources, but nothing was mensioned by Eric Gorr. I never asked him how to break it in because I have never had a problem doing it the way I do.

No matter what bike it is, no one can tell you exactly how to perfectly jet the bike because of differences in the bike itself, temp, altitude, fuel, mix oil, the way you ride, humidity, ect. But, a good starting point is important. On stock bikes, the manufacturer gives us a starting point with the stock jets. Most of the time a stock bike runs rich and needs to be leaned out. With the 144, there is no starting point other than what people like Eric Gorr, WAMXP1MP , and others that have had the same mods find that work. With my bike now running very rich, I would say that a good starting point would be a 450-460 main, 2007 needle on the 3rd or 4th clip, and a 45 pilot with the air screw around 2 turns out. I am hoping to go riding on Sunday, and will do some testing and report back. I am currently running the stock needle in the 5th clip and a 40 pilot with the air screw a little less than one turn out. I think the main reason for the rich condition is the needle in the 5 clip.

By the way, I would keep the stock plug heat range (br9es I think) and run 32:1 ratio and jet from there. I would not change heat range or ratio to fix jetting problems. Run consistent. Same plug, same mix oil, same ratio, same fuel, and jet from there.

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Okay, Finally going riding this weekend. I did a little more work since I got the 06-07 needle. I put the needle in set at the 4th clip and warmed the bike up. Pilot is the stock 40. Air screw stops raising the rpms around 2 1/2 turns out. The bike is starting to clean up, but there is still a ton of smoke puring out of it. It doesn't smoke too much at idle, but when you goose the throttle and let the rpms drop on their own, smoke just pours out. The plug is black but dry. I then moved up the needle to the 3rd clip because I figured when goosing the throttle, I am getting past 1/8 throttle. Riding the bike (in the limited area I have), is incredible. Leaning out the pilot screw made a huge difference. I can quickly crack the throttle (a crack that would cause my 250f to bog) and the rear wheel spins or the front tire rises ( very quickly) in both 1st and 2nd. I was messing with getting the air screw correct so i would give it a 1/4 to 1/2 turn then ride it. Once the pilot circuit cleaned up around 2 turns out, I almost lost it. I cracked throttle thinking it would be a slight improvement, but there was little to no delay in the response. As fast as i could snap the throttle, the power went right to the rear wheel. The front wheel went past the balance point and I just managed to save it with the rear break. Keep in mind this is with no clutch use. I am running in to some evidence that I am too lean on the pilot screw because the idle is starting to hang up a little. I will continue to report back when i have more.

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