Performance doors have opened for 2016-18 Raptor 90! - Yamaha Raptor Forum
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post #1 of 9 (permalink) Old 10-29-2018, 07:48 PM Thread Starter
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Performance doors have opened for 2016-18 Raptor 90!

Hello all!, i recently purchased a 2018 raptor 90 for my son to start racing with. it became clear very quickly there was no aftermarket support for this bike. HMF and big gun offer exhaust but that was about the extent of it. so i contacted a "well known" bike performance shop who said to bring it in and they will do a high compression piston and head porting. Well after 6 weeks of run around from this shop, i picked my engine back up and took it to a local builder who specializes in smaller 4 stroke atv, dirt/pit bikes. 15 min after dropping the engine off and him pulling the top end apart and taking a few measurements with a mic, while i was standing there he said the options are wide open. Apparently yamaha or whoever builds the new generation engines converted the stud pattern to a Honda stud pattern. He went through several options i had as far as piston sizes, **you can only bore stock sleeve 3mm before needing to bore cases if you wish to go any bigger than a 50mm piston and you will need a larger diameter sleeve as well obviously. but there are options to build this thing well over a 125. Next was head work, the stock heads flow terrible from his explanation and even porting them you were better off to look at other heads that dont cost much more than a quality port. We settled on a V2 race head with perfomance cam. This is just the beginning of options. i could have went with a larger roller rocker head which would have allowed for a domed piston bumping compression. so all said and done i settled for a 50mm piston (stock is 47mm and i didnt wanna tear into the cases at this time to go larger than 50mm), v2 race head with performance cam and larger valves and mikuni vm22(which i had already). After some jetting my son has a raptor that RIPS! the low-to mid range gains were impressive!. ***now dont go and buy these parts thinking your gonna slap a head on and go, there was some machine work that had to be done on the new piston to clear the larger valves as the 50mm piston is more of a flat top. Any questions feel free to ask, this is huge news in my opinion for this bike that has been pretty much considered a useless competiton bike. Not for older raptor 90's, 2016-18 and i would imagine the 19's as well
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post #2 of 9 (permalink) Old 11-10-2018, 02:48 AM
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This was very interesting.
Were dig you find a 50mm piston?
Im doing a 26mm mikuni upgrade.
What exhaust do you have?
Rev limiter?


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post #3 of 9 (permalink) Old 11-12-2018, 01:40 PM Thread Starter
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I’m not sure where my builder sourced the piston from but a quick google/eBay search turned up several 50mm piston options. As far as exhaust goes We’re running a full hmf, rev limiter is stock cdi, I think a 26mm carb will be way over kill if your using stock head, the 22mm was difficult to jet with the stock head, not saying it’s impossible but if you don’t have an assortment of jets and needles laying around it will get frustrating lol
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post #4 of 9 (permalink) Old 11-12-2018, 01:52 PM Thread Starter
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Here’s a couple pics of a spare 50mm piston that I have that is identical to the one we put in the bike
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post #5 of 9 (permalink) Old 02-15-2019, 07:34 PM
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Sure would like to know how your 90 is doing without a high rev cdi box? My son races a 2018 90 and with the HMF pipe and a modified air box, he is hitting the stock rev limiter all the time. It's really holding him back.
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post #6 of 9 (permalink) Old 02-15-2019, 07:45 PM
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Quote:
Originally Posted by CrpntrFreak View Post
Sure would like to know how your 90 is doing without a high rev cdi box? My son races a 2018 90 and with the HMF pipe and a modified air box, he is hitting the stock rev limiter all the time. It's really holding him back.
You could always add 1 tooth to the front sprocket, or reduce the rear by 1 or 2 teeth.

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post #7 of 9 (permalink) Old 02-15-2019, 08:05 PM
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Originally Posted by CrpntrFreak View Post
Sure would like to know how your 90 is doing without a high rev cdi box? My son races a 2018 90 and with the HMF pipe and a modified air box, he is hitting the stock rev limiter all the time. It's really holding him back.
You could always add 1 tooth to the front sprocket, or reduce the rear by 1 or 2 teeth.

WELCOME TO THE FORUM.
I thought of that. May be the way to go. I understand that he'll never be able to keep up with the DRRs and the Apex quads but every race one of those quads are breaking down. Being that I am a carpenter trying to be a race dad, I'm at a huge "mechanic " disadvantage. Lol. The Raptor has been flawless and I'd like to keep it very close to that.

Thanks for the welcome!
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post #8 of 9 (permalink) Old 04-09-2019, 07:36 AM
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Where did you find the jets for the stock carburetor. What type of jets are they I can't seem to find them anywhere.
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post #9 of 9 (permalink) Old 04-09-2019, 09:14 AM Thread Starter
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Sorry i haven’t been on in a while, to answer the most recent question about jets in the stock carb, we ditched that carb and went to a mikuni vm 22, however after hours of tuning it an rejetting , these motors just don’t have enough low end air movement to correctly pull the fuel for idle and early part of needle circuit resulting in a lean bog, I just purchased a 20mm aft carb from tbparts.com and some jets to correct this issue.

The next question about stock cdi limiter, yes this was an issue, we went with a cheap after market eBay setup, one of the no rev limit deals, I recommend getting the one with adjustable timing as the timing curves are close but not exact to the stock cdi, VERY IMPORTANT- make sure the cdi you buy is a DC cdi box, do not buy a AC cdi box as it could damage your system. The 16-19’s are different than earlier models so don’t buy a cdi listed for one of these earlier models. We also increased the front sprocket size, going one tooth up in front is like going down three in the rear I believe, I would only go up one or two teeth in the front and see how that does. We only went up for one now but have clean up to a 17tooth front sprocket that I haven’t tried yet because you will need a longer chain and I’m waiting for ours to wear out.

We also have no chance of catching the top two dogs in My sons class as their apex 90’s are built to the moon and and honestly should have a class of their own, however 3rd through 7th place is a always good and fun battle to watch. FYI we are the only four stroke and the rest are two strokes. If the two stroke is a stock deal and your bike is properly setup you can beat them. All comes down to the rider as well.
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