Opinions on my temperature.

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eclark5483
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Opinions on my temperature.

Post by eclark5483 »

So, on vacation this week, decided to do a nice romp on the scoots with my daughter and son. Did a nice long country drive around the outskirts of town. Checked my CHT temp gauge to see the max temp it was running on this hot day, and I showed I hit 192 Celsius (377 Fahrenheit) at peak. This was after traveling 45mph+ for about 5 continuous miles. Not quite WOT the whole time, but pretty dang close.

So is 377 too hot, or is that right about where I should expect it to be? I didn't notice any problems, sputtering, bogging, etc, but I like to play it safe to keep the engine healthy for when my boy uses it.

I expect that will be the range it runs in after I get the ported BBK installed as well, just wanna double, triple check, and get opinions on temps before attempting the next dyno run this fall. Shooting for 57mph dyno run on non variated AF05.
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Re: Opinions on my temperature.

Post by Dallen70 »

Just go up a main jet if you're doing a lot of wot riding
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Re: Opinions on my temperature.

Post by eclark5483 »

Don't know that I want to do that if my temps are within range. Would be silly... as the saying goes... If it ain't broke, don't fix it. It has already taken me over a year to get to the point where I am now. I don't think a higher main is gonna make much of a difference, in fact, it might even make it bog a bit from being too rich.

I follow the general rule of P+M=132-135@70cc (68cc/48mm BBK) I.E. 34 Pilot+100main. Tuning wise, and dyno values show this is giving me the very best stoich A/F all around. Somewhere in the 12-12.5 range. So I know my mix/combo is working perfect on tests and in the real world.

The issue, is I am going to attempt to push the Spree to 12,000 rpm, which probably, yes, means a jet upgrade. For now though, I need to examine the data I am getting when I use the bike under intense riding like WOT.

Thankfully, no soft seizing yet, no running issues, but the high temp has me asking questions like... is that TOO high, or is that normal for 89 degree heat driving WOT. If it's normal then it just eases my mind a bit about the next phase. I don't go 100% WOT much for 2 reasons... 1. I'll pass my daughter and she peaks in at around 47mph (GPS), and 2. I'm too chicken to stress the engine for extended periods. I think peak rpm I dared take it to, was like 11,200 or something like that. I am assuming a mere 800+rpm to take it to 12,000rpm will make more heat, which begs... how hot is too hot?

edit: SIDE NOTE... I'm also kind of thinking of drilling out the tranny cover so it gets more air to the belt/clutch, might pick up a mph or 2 doing that, still dwelling on it.

Ideally, I would want my temps to be at 12,000rpm what they are at around 10,000, which is... I wanna say, around 180C/360F. If I can maintain that temp at 12,000 WOT, I'd be happier.
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Re: Opinions on my temperature.

Post by Gearhart »

Why ask the question if you already think you know the answer? Seems silly to me. Personally I wouldn't run that spree bbk anywhere past 370, I would try to keep it below 350. Those bores aren't made with the precision tolerances of an Italian bore that people will push up past those temps. You're playing with fire getting it any hotter than that IMO.
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Re: Opinions on my temperature.

Post by eclark5483 »

See, that's what I am wondering. Seemed to me as well that 350 or lower is where I want to be, but then I have also have heard others say 370-380 is normal?? When ran casually, at say around 40mph or so, it doesn't do too bad. Right there your talking around 8,000 rpm. 9,000 is not so bad either, or even 10,000. At a guess, I'm in about the 360 degree range at 10,000. The difference on the throttle isn't much. It's really a matter of pushing back about 1/4 throttle for wide open. One thing I noticed, is you can't simply throw back the throttle and reach 10,000+. You have to find a nice sweet spot past 35mph and slowly increase the faster you go... I.E.. you're doing 38, you go back a slight bit more till you get to 39-40, then a bit more, and etc, etc.. I am assuming this is because of the lack of CVT. It's much different on the dyno. There I can take it and throw the throttle back and it will climb up to it's peak.
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Re: Opinions on my temperature.

Post by Wheelman-111 »

Greetings:

Resistance to acceleration on the dynamometer is linear. Resistance on the road rises exponentially with wind speed. That may in part explain why you have to nurse the throttle to reach maximum velocity, but it sort of implies wonky jetting near the peak RPM. Whacking the throttle open all at once makes the mixture lean, briefly, because you reduce venturi vacuum - lower the value of negative pressure. Vacuum only returns as the RPMs increase, and if you're very LEAN, the power goes down and it won't increase. Speed may even drop. Temps for sure will rise.

Along with your high-ish temperatures, all this suggests you may be just a tad lean overall. Probably not a full jet size, but just a little. If you have a few stock jets lying around, you could try indexing your jet size and reaming a few out - just .01mm at a time, trying various mods until throttle response returns to linear. Another option is to play with jet needle thicknesses, but without a selection of those (Like Keihin makes...) that'd be considerably trickier.

Jetting isn't the only to change running temperatures. You can gut the fan screen, add a scoop, and make sure your shrouds aren't wheezing air out the cracks and spark plug boot. Aftermarket High-Output Spree fans probably don't exist unless you design and make one... I've had a Nikasil bore get to 550F. on the CHT gauge and didn't grenade, but I've had a (rookie) Tai bore seize at 300; There's no telling from temps alone what might cause damage, but 400 or more causes Wheelman Puckering. This is a fun discussion.
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eclark5483
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Re: Opinions on my temperature.

Post by eclark5483 »

Yeah, I have extra jets, so that's no issue there. I haven't attempted any higher yet simply because it's running so well. Currently running a 34 pilot and 100 main. Just seems that a 100 is already ridiculously high, but then, guess I won't know till I try it for myself and see. The displacement math tells me that should be close to right. Guess I never considered that temporary leaning when you blast the throttle. On my daughter's 4 stroke with CVT, it's a deal where you start going, blast that throttle back, and you just keep picking up and picking up till it peaks.

I have a kit of 100-118 Polini jets, thank you Wheelman, you have convinced me to try bumping it up more and see where that takes me. I don't mind playing with the throttle to get to peak, but if I can solve that plus the questionable heat all in one shot, that would be sweet.

Longterm, I will be replacing the current BBK with one that was ported by 1man, but I wanna get my tunes/heat worked out first before I put that bad boy in. I don't drive the Spree much, I'm usually riding the motorcycle and my boy is driving the Spree, but I like to get on it every once in a while with the kids and wife and do some family scooting for fun. If you ask my kids, it runs great, but then it's not easy to get a proper assessment from kids with Autism so I gotta find out for myself. I honestly attributed nursing the throttle with me being a big guy. My daughter gets on it, she just zooms right off.. When I ask how the throttle is, she says it's OK. My son will MAYBE go 15 or 20 on it and that's it, so obviously he never pulls the throttle back much.

Sooo glad though that I had that tach/temp gauge installed. Makes noticing and isolating potential probs so much easier.
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eclark5483
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Re: Opinions on my temperature.

Post by eclark5483 »

Wheelman-111 wrote:This is a fun discussion.
Yes it is. We are talking about a more high end, higher RPM type situation that most Spree owners will never encounter. I'm beyond getting the BBK to run well, and have found myself in the more "advanced" engine tuning. I have the backup engine, no prob, but would rather hear input now from data I give to help optimize more. Obviously, Taz's BBK hasn't blown at 377 degrees, but the question is, is this a normal temp, or can I fix it with jetting? Dang, how I wish there were others with configs like mine to sort it all out!!
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Re: Opinions on my temperature.

Post by Wheelman-111 »

Greetings:

Quoth eclark:
how I wish there were others with configs like mine to sort it all out!!
That's what makes Pioneers like yourself so valuable to the fund of knowledge in the Forum Collective.
I actually had a 24mm Keihin CV carb on one of my builds. I had to make my own cable because the butterfly primary throttle had a snail connection. The vacuum-controlled secondary slide won't open until vacuum returns, and the 2-stroke 78cc actually ran pretty well with it. But forget about asking anyone what jets to use... AFAIK no one else ever installed one.
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"ISO": '03 Vespa ET4 Malossi187 74MPH
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