Does anyone use a longer rod in any big bore that they have done? Is there anything to gain or does a big bore not need it? I was thinking of trying an 03 CR 125 there are so many options and not enough money in my bank account the stroker idea is out $$$ eric changed my thoughts on that real fast. any help is appreciated.
long rod 134 144
- Thread starter hot125mod
- Start date
stumanarama
Member
- Aug 29, 2007
- 306
- 0
length of rod does not affect stroke, that would be the crankshaft
2strokerfun
Member
- May 19, 2006
- 1,500
- 1
The longer rod will generally slow the speed of the piston near the top and bottom of the stroke and speed it up in mid-stroke. If you do this, you'll have to raise the cylinder up the same amount as the rod increase. The result would vary greatly, depending on the engine and length of rod increase.
The better question is: what are you trying to accomplish with your engine. Once we know that, some of the gurus may have suggestions to get you there. Increasing the rod length just to increase the rod length will get you nowhere expensively.
The better question is: what are you trying to accomplish with your engine. Once we know that, some of the gurus may have suggestions to get you there. Increasing the rod length just to increase the rod length will get you nowhere expensively.
- Thread starter
- #6
you guys answered my question exactly i am not sure what i was trying to accomplish but i want to get the most hp out of my big bore what ever it ends up being. so should I just use the stock rod or do the base plate and a long rod? i want a 250f killer I just wanted to try more than just a big bore but the ammount of gain that is there is not really worth the money tho get 10ccs from a 2mm stroke on the crank. so here I go again chasing my tail will it be eaiser to keep on the pipe with the longer rod or what is the seat of the pants feel on it if any? is the rod length only something you would see on a dyno. too minimal to actually feel? I want this thing to breath fire and strike fear into those who choose to ride bikes with valves hahaha j/k
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My son and his friend have identical rm125 both 05's. We went with an EG 144 ( about $500) His friend went with a local builder that makes the 144 by boring and stroking ($1500). My sons bike is alittle faster on the straights and a lot more grunt in the corners. Both bike have v-force reeds and stock pipes. Their jetting may be a little off. Riders are same height, weight and ability and practice at the same track.
If you are a novice rider forget everything and use your time getting your bike jetted right and riding. Spend your money on lessons and fuel.
Or find a club that will actually go by ama rules and buy a 250 2t for the lites class
If you are a novice rider forget everything and use your time getting your bike jetted right and riding. Spend your money on lessons and fuel.
Or find a club that will actually go by ama rules and buy a 250 2t for the lites class
- Thread starter
- #8
if I decide to do a cr 144 do I need to have the cylinder grooved since the hondas use a metal head gasket. I heard that their cylinders are not flat from the factory and need to be lapped or is that just on the 80/85s also the orings hold the higher compression better. I would like to get as much compression out of it as i can and have it last at least a weekend. or even be solid for 1 race or is that asking too much. suggestions? :think:
- Thread starter
- #9
my jetting skills are pretty good i just tinker too much and probably just chase my tail too often. are the mikuni carbs more difficult specifically the TMX 38s than a pwk 38 or are they even. one more thing are you likely to rebild more often if you use Ultimate 2 or is that not an issue. of course the jetting is changed
dirtbikr99
Member
- Nov 21, 2002
- 180
- 0
dude, listen to me. Take the money you are thinking about spending on big expensive performance mods and replace all the worn out parts on your bike. For example Tire, chain and sprockets, air filters, grips, brake pads, and so on. Do not use expencive vp racing fuels because your stock engine does not need it. Use all the extra money on gas for the bike, gas for your truck to get to riding spots. Ride as much as possible! Improving your riding skills will help you out at the track much more than spending alot of money on engine mods. Oh and by the way I had an 02 cr125. I rode it in stock form, then again with cylinder porting/134cc big bore. The 134 big bore was a noticably faster bike but nothing night and day. The 250f's are still faster, and much easier to ride because they have more low end power. Another thing to note, I also had both the front and rear suspention revalved. The suspention work seemed to help out on the track more so than the engine work. So in conclusion, Save the money you were going to spend on performance mods and use the money more wisely. Just ride alot and improve your riding skills. Dont have the mentality that performance mods will make night and day faster on the track because it wont. Only hard work practicing! :) And.....I am no expert by any means!
Last thing, If you do decide to do engine work, I hear great things about eric gorr.
Last thing, If you do decide to do engine work, I hear great things about eric gorr.
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hot125mod said:
Then build the bike that will be the most fun for YOU, and try to take some of these "experts" with the appropriate sized grain of salt. ;)
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bclapham
LIFETIME SPONSOR
- Nov 5, 2001
- 4,340
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for a 144, its always best to start out with the best bike.
the YZ125 is THE best bike, it makes a great 144.
the RM125 is also a greta engine (KTM copy) it also makes a great 144- since its a top end screamer, it really benefits from the 144 since it gains bottom but still has the ability to rev well, and it uses a long rod, LOL.
the YZ125 is THE best bike, it makes a great 144.
the RM125 is also a greta engine (KTM copy) it also makes a great 144- since its a top end screamer, it really benefits from the 144 since it gains bottom but still has the ability to rev well, and it uses a long rod, LOL.
- Thread starter
- #16
yeah thats what I just remembered the rm and ktm are twins alright I need to get rid of my bike so i can start hunting for new victim thanks for the help as always anybody from minnesota in here just curious. Now i need to figure out a new race juice mix I have been wanting to get a hold of Dr. Dave to come up with something or I could just stick with U2. gotta love that oxy
