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Discussion Starter · #1 ·
New 250r owner here looking for some advice on what direction to go with an engine build. This is a long-winded post, so I will say, my main question is contained in the second paragraph. The rest of this is just supporting information for those interested in knowing why I'm looking for the type of build I am, specifically.

I'm wanting advice on options for a GNCC/XC type setup with a very broad powerband, & an emphasis on low/midrange much more so than top end. I have one odd requirement in that I need the build to run on either 92 octane pump, or 100LL AVGas (100 octane), as where I live (far Northern California), race gas is unavailable for purchase within a 170 mile radius. For that reason alone, I'd love to do a lower compression build for 91-95 octane if possible - but that's not an absolute requirement at all.

I've spent hours reading countless threads online, but have found that 90% of people's builds are more suited for dunes/desert high rpm builds, unsuitable for my application, which is why I've started this thread.

A little more about myself, my riding area, & what I'm looking for out of this machine:

I ride mostly Pacific Northwest style slow, steep, technical trails mostly, which is why a very broad powerband & a ton of low end torque is desired rather than the usual high strung screaming top end sand builds that seem so common. Some might say "you don't need a huge big bore or tons of power for that." Being a pretty experienced rider & a power junkie to boot, I tend to disagree strongly with that statement in most cases.

I ride primarily big bore 2 strokes. CR500s. I'm also 220lbs. Having ridden those bikes for so long, I tend to short shift a lot & rely on the low & mid range to carry me through slow, technical sections. For reference, the broad power curve of a CR500 is exactly what I'm looking with this build. Obviously, I realize getting CR500 power levels & delivery on a 250r is not a simple task, but that's the ultimate target.

My machine currently has a CT ported cylinder with 38mm PWK AS, I THINK a CT national pipe & silencer, & a high compression head cut, running around 215psi compression & 100LL AVGas. Supposedly bored to or around 270cc according to the previous owner. This engine combo runs great, but is nowhere near the low end power levels I'm looking for. It's actually fairly dead on the bottom & pulls hard out of the upper mid range, which seems odd if my pipe is indeed the CT "National" as I believe it to be.

I've contacted LED, ESR, & CT & asked their thoughts. Arlan recommended his Puma 430 setup & said 100 octane is the absolute minimum on any engines he builds - no pump gas. Eddie recommended the 330 kit for pump gas, but simply told me he's out of cylinders, so no engine packages are available anyway. Allen recommended his 350 powervalve setup with 2 head domes (one for pump & one for 100 octane) & said that will check all my boxes. He also elaborated to say he used to offer a 410 kit but he stopped because they were very hard on our 30 year old transmissions & said he has the option of offering the Puma setups, but he doesn't because he does not like the power curve.

The build I've seen at least in videos that really caught my attention is a guy Justin Sturgill Trucking on YouTube. His bike has a 379 CEO setup built by Arlan & has very broad torque according to Justin & another YouTuber who rode it, Michael Sabo. I mentioned that build to Arlan when contacting him, but he still recommended the Puma 430 over that build, for my needs.

I certainly trust these guy's opinions on what would be most suitable for me, but with the variance in recommendations, specifically Arlan recommending Puma but Allen saying he doesn't care for the power curve + recommending against massive big bores vs my old transmission, I'm kind of still left scratching my head....

If any of you guys have been down this path, or simply could provide feedback on your build, different engine combos you've ridden, or other options even, would be greatly appreciated.
 

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My first question would be what is your budget? Any massive big bore type setup like that is going to run 5-7K for just the motor, especially if you replace the transmission with Arlan's Billet trans - could be more.

I always ran tight trails and found a 250-275cc to be enough with the right pipe and intake. However I am not 220lbs and am not used to the power of a 500cc. So I think they are leaning you in the direction of big bore vs what is needed/suited for your riding. I think realistically a 350cc should be fine, especially with an older transmission. I also think that in low rpm, you may want less mass on the piston because the counterbalancer is only so big.

If big power is what you want, maybe you should ditch the 250R and order a 500cc Panthera motor and pop it in the 450R. The 450R chassis might even suit your frame a little better. I've always found the 250R to be small for big guys - it will also tend to crack and break the frame with a big guy and big motor. Buy Motorcycle Engines online | Panthera Motors.

Guys with Puma's could chime in with a better understanding, but from what I gather, both the ceo and the puma are built for mid-top ends. If you weren't so focused on power/big bore, I'm surprised Arlan didn't mention the idea of just going with a 300cc resleeve of a stock cylinder and porting it properly and building a custom pipe.

What are you starting with build wise? What is your budget? With your weight and power requirements, you are going to want a lot of aftermarket and chromoly stuff because you will destroy anything stock. I'd say you are 15-18K for sure these days.
 

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Discussion Starter · #3 ·
What are you starting with build wise? What is your budget? With your weight and power requirements, you are going to want a lot of aftermarket and chromoly stuff because you will destroy anything stock. I'd say you are 15-18K for sure these days.
Excellent info & I very much appreciate the detailed response. Budget is flexible. I'm expecting conservatively to dump around $4-6k into the motor itself + another $2k (or more if necessary, depending on setup) for pipe, possibly ignition & other supporting mods.

That said, realistically, I do not need a 75 or 80hp monster, but I'd love to get around 60-65hp range. Allen told me to expect 57-58hp out of the 350PV. I could live with that, but it's not quite what I think I want. But, the broad powerband requirements supercede raw dyno numbers for me, without question. Reliability does to a degree as well. In order of importance to me: broad powerband, reliability, power. But all 3 are very important.

Another thing I actually didn't think of is trying to kick start a monster big bore setup. I can kick CR500s & YZ490 etc no problem, but I did read some guys saying the huge 250r big bores can be a nightmare to start. Any feedback on that is certainly welcomed there.

The machine I'm starting with has a lot of stuff done & a good amount of money invested already, but I certainly will be upgrading & changing a small handful of things to get it set up how I want. It's an 87 model with stage 3 elka & lots of bolt on parts. Still running stock swingarm & A arms which I'll be stepping up probably to +1 lonestar or equivalent, for both. This is a machine I intend to keep forever so no problem spending a good bit of money on it.
 

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imo dont do the puma.too much money for what you get.if you can find a ceo391 or 363 they work great. but as you said esr is out of cylinders.so your last choice in a 363 sphynx,or lynx would be a great combo.
 

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Discussion Starter · #5 ·
imo dont do the puma.too much money for what you get.if you can find a ceo391 or 363 they work great. but as you said esr is out of cylinders.so your last choice in a 363 sphynx,or lynx would be a great combo.
Thank you for the info & suggestions. Doing more & more research, I'm beginning to feel like the Puma 430 might be a good bit overkill even for a power junkie like myself, for what I will be doing with this machine. I've also noticed that some/most the 400cc+ builds are running huge drag style pipes. For my XC style build, I would definitely need an in-frame style pipe, which makes me wonder if I'd be leaving a lot of power on the table & never see the true potential of those really big motors with my configuration, anyway.

But from what little I've been able to find & read about the 391 CEO setups, that seems like it might be a solid choice for me. Hopefully ESR is able to come up with some more cylinders before too long. I don't mind waiting awhile to get the setup that will best suit my needs.

I've read some of your threads & saw you've had opportunity to run quite a few different combos. How does a 363 setup compare to the 391 in terms of power curve? I've read some guys saying the 363 is more of a peaky top end WOT motor vs a 350. Allen also mentioned to me that CT's 370 setup would be less suitable for me vs the 350 for the same reason...
 

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Discussion Starter · #8 ·
CEO 391 is sounding more & more like exactly what I'm looking for... Does anyone know the exact bore + stroke for the 391? Also minimum octane rating or compression readings from that setup? I can't find a lot about 391 builds online, just 350 & 363 mostly...

As stated already, I'm regulated to 100 octane (some people say it's closer to 105) 100LL AVGas at best for any build I run. My current CT ported stock cylinder with a couple short rides on the motor registers 215psi & seems to run fine on 100LL & 40:1 Motul 710. I'm intentionally jetted a little rich & might move to 32:1, but running now with no noticeable/detectable detonation far as I can tell.

That said, I don't want to turn this into a "builder-bashing" thread but at the same time I have to be totally honest about something that's left me a bit confused, & definitely disappointed + surprised. I called CT simply looking for base jetting advice. The lady who took my call outright refused to let me speak to Allen (even after telling her that Allen in email told me to call him) & was pretty rude & condescending, speaking to me like I'm asking way too much & need to be scolded like a disobedient child, before finally giving me some seemingly very simple info/assistance. I honestly remained super polite, but for some reason she was actually borderline confrontational. But anyway, she told me the following:

That my motor's 215psi compression is super high, that engines with that high of compression often are set up for alcohol, & that I MUST run 110 octane minimum. She also told me my Matco compression gauge might be inaccurate, which it's definitely not (I worked as a mechanic for 18yrs). While I certainly recognize my 215psi is starting to get on the high side of compression, I'm not so sure about the statement that I need 110 octane as a minimum... I'd welcome input on the validity of her statements.

Thank you guys for the info, as it's definitely helping steer my decision!
 

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I recommend a 370 with a stock stroke. By far the best I have ran. I have had more engine combos that most and have spent the last 6-7 years racing woods. The big bore stock stoke 370 pulls very strong down low while giving you lots of flexibility at higher RPM. I have a 363 stroker in my MX machine, and if I did it again I would put a stock stroke 370 in it again.

Arlan at LED performance did mine with a ESR cylinder. Couldnt be happier with the setup.
 

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Discussion Starter · #10 ·
I recommend a 370 with a stock stroke. By far the best I have ran. I have had more engine combos that most and have spent the last 6-7 years racing woods. The big bore stock stoke 370 pulls very strong down low while giving you lots of flexibility at higher RPM. I have a 363 stroker in my MX machine, and if I did it again I would put a stock stroke 370 in it again.

Arlan at LED performance did mine with a ESR cylinder. Couldnt be happier with the setup.
Thank you! Allen at CT told me their 370 kit is more of a top end motor suitable for dunes & flat out desert type racing. Does yours have a PV?
 

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Depends on what 370. Mine is a 81mm bore, and has all the grunt in the world. Here are some videos with some proof of the holeshot potential. I used to run 235 compression, but ended up dialing it back down for my 10 hour long race to 190. I usually rebuild the top end around 25 hours, just because Im between races seasons. Havent had one actual fail on me yet.




 

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I should clarify my friends ESR 391 isn't the CEO cylinder... A 370 is basically a 391 without a stroker crank & pretty much any big bore can be set up for bottom/mid if it's done right.
 

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Discussion Starter · #13 ·
Haha those videos are awesome. I love seeing modern 4 strokes getting beat up by a 250r, especially while pulling a nice wheelie way out in front of them. Thank you for sharing!

& Thanks for the info as well. A few questions for you Burns350R. Is your build CEO or standard piston? Also power valve or non power valve? At 190 psi compression, what fuel are you running in it?

Also, you mentioned you've had a lot of engine combos. Have you had or ridden a 391 (CEO or standard) & have any insight as to how it compares to your 370 in regards to power delivery/curve?

I appreciate all your guys' time & knowledge in helping guide me to the best setup for my needs.
 

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Mine is not a CEO, I have not ridden one. I hear they are great. Honestly for what I'm doing I dont need any more power. Im a bigger guy at 6'1" 220lbs and I have no problems pulling the wheels through the first 4 gears even with tall tires and gearing. Thats more than I will ever need in the woods at the A class level. I also know for a fact there is more power available if I needed out of this combo.

I do not run PV motors, I have had some and never liked them for higher RPM pull, My PV engines where early ESR design, so they may have improved, I always thought the PC cylinder style looked a little better with the larger diaphragm. Either way I have lots of bottom/mid range power now and less moving parts.
 

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Discussion Starter · #15 ·
Im a bigger guy at 6'1" 220lbs and I have no problems pulling the wheels through the first 4 gears even with tall tires and gearing. Thats more than I will ever need in the woods at the A class level. I also know for a fact there is more power available if I needed out of this combo.
Thanks very much for the input. It sounds like you're pretty close to same size as me, & after seeing your videos pulling holeshots & power wheelies way in front of the competition, it's obvious that engine absolutely rips!

I haven't been able to get Arlan on the phone yet (I'm sure he's very busy) but Pete @ Hybrid Engineering gave me a good amount of his time yesterday & answered every question I could throw at him. He advised me to stay away from 100LL AVgas all together & just set up my build for pump gas.

A couple more questions for you if you don't mind, Burns350R. You mentioned dropping your compression ratio down to 190psi. What fuel are you running at that compression? Also, did you notice any significant drop in performance or power delivery characteristics of your engine after lowering your compression? Do you mind sharing what pipe you're running? What ignition system do you have?

Pete recommended LED 350G pipe & 2001 CR125 or CR250 ignition for my application, but I've been reading some people don't like the CR ignition for woods riding, due to the much lighter flywheel. Any input or experiences with that would certainly be welcomed!

Again, thanks very much to all for your help & guidance!
 

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I run Sunoco 110. I didn't change fuel, as i buy it 55gal at a time. My main concern was less wear and tear on the engine for my 10 hour long race. Rather not strain anything when I know I wasn't going to be using the power at the later hours in the race.

I didn't actually notice that big of difference, that being said you almost never use all the power in the woods. It the 370 would actually make more power with a 350g pipe, I run the 350g on my 363 stroker on my MX build. I like the longer smoother power band of the 350d pipe on my 370. again the engine makes such good power, I wasn't trying to make peak numbers as much as low end grunt with the ability to over rev nicely.

I run a CR ignition on my 363 with a flywheel weight. The weight is makes it a lot better. I ended up going back to a stock ignition with a modified harness on my XC machine because part of the 10 hours is ran in the dark. Again, there might be some slight difference in peak numbers, but the power is plentiful and I wasn't looking for a peak number. I had a CR ignition on it, and it worked good, I could see it being a bigger deal if your looking for every last number on the dyno.
 

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Discussion Starter · #17 ·
I run Sunoco 110. I didn't change fuel, as i buy it 55gal at a time. My main concern was less wear and tear on the engine for my 10 hour long race. Rather not strain anything when I know I wasn't going to be using the power at the later hours in the race.

I didn't actually notice that big of difference, that being said you almost never use all the power in the woods. It the 370 would actually make more power with a 350g pipe, I run the 350g on my 363 stroker on my MX build. I like the longer smoother power band of the 350d pipe on my 370. again the engine makes such good power, I wasn't trying to make peak numbers as much as low end grunt with the ability to over rev nicely.

I run a CR ignition on my 363 with a flywheel weight. The weight is makes it a lot better. I ended up going back to a stock ignition with a modified harness on my XC machine because part of the 10 hours is ran in the dark. Again, there might be some slight difference in peak numbers, but the power is plentiful and I wasn't looking for a peak number. I had a CR ignition on it, and it worked good, I could see it being a bigger deal if your looking for every last number on the dyno.
Once again, you've come through with great info & feedback for me here. I really appreciate you taking the time to answer my questions & provide your insight. I'm thinking I would likely be happy with any of the setups you've mentioned. Parts availability may end up being a determinating factor too, it seems.

That said, I don't mind waiting awhile - but it also kind of seems like a gamble whether or not the ESR cylinders & other parts necessary for those builds will become available again any time in the foreseeable future. The way things have been, I'm not sure how much faith I can put into that.

After talking with Pete, I'd absolutely feel comfortable having him complete my build, but he's also affected by the current parts shortage. So still hoping to hear back from Arlan to see what he might have available, if anything.
 

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Once again, you've come through with great info & feedback for me here. I really appreciate you taking the time to answer my questions & provide your insight. I'm thinking I would likely be happy with any of the setups you've mentioned. Parts availability may end up being a determinating factor too, it seems.

That said, I don't mind waiting awhile - but it also kind of seems like a gamble whether or not the ESR cylinders & other parts necessary for those builds will become available again any time in the foreseeable future. The way things have been, I'm not sure how much faith I can put into that.

After talking with Pete, I'd absolutely feel comfortable having him complete my build, but he's also affected by the current parts shortage. So still hoping to hear back from Arlan to see what he might have available, if anything.
I would give him another call at the shop.
 

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Discussion Starter · #19 ·
I would give him another call at the shop.
I took your advice, called the shop again & had a good discussion with Arlan. I mentioned I had been in contact with you & that your setup seems like it could be suitable for me. I was a little surprised to hear his input, as he felt the 370 would not produce the power levels & delivery I'm looking for. But also said he's not doing any more builds with ESR cylinders, now or in the future.

Arlan recommended the Puma 408 for me after speaking with him a bit. He said the power delivery & rpm it peaks at is very similar to the CR500s I've been riding for years. He also mentioned that some advancements have been made with the Puma setups & said whatever I might think or know about the Puma stuff could be much improved now.

Decisions, decisions...
 

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Glad you got ahold of him. Im surprised that he says that it wouldn't have the low end power. But hey things have changed in the past couple years since I started running my setup. My guess is you will be happy no matter what route you go. I know Arlan has delivered every time I have worked with him. Keep us posted which direction you go.
 
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