• 2 Stroke Husqvarna Motorcycles Made In Italy - About 1989 to 2014
     WR = 2st Enduro & CR = 2st Cross

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250-500cc Wr300 compression ratio what octane

Tommy V

Tommy V

Husqvarna
AA Class
Ok, crazy idea but will the WR300 start easier with a lower octane fuel? The compression ratio is listed as 6.9:1 which seems really low when you compare it to say, a YZ250 with is around 10.9:1
My YZ ran like crap on anything short of premium with a 20% mix of VP
My WR300 runs great on Shell premium but I'm wondering if the higher octane is actually in part responsible for the finicky starting everyone complains about.
I am running a 36mm Lectron and it's pretty dialed, I always turn the lights off and even in neutral, the bike is a pain in the ass at times. I always make sure to lean on a tree or the side stand so I can stand on the peg and kick but on occasion I will stall it and don't have the option. I can get it started but my knee hurts for a week (torn meniscus) and I. Trying to avoid surgery
I am close to selling the bike for this reason alone. I love it otherwise. Looking for any other tuning tricks to make it fire up easier.
Has anyone tried mid grade or (gasp) even regular in their 300?
Remember, high octane equals slower burn and even less power unless the compression ratio is high enough to match the octane
???
 
Out here in the west, we have some pretty low octane premium...and it has alcohol in it too. That's what I run. I'm kind of short, and I have bad knees, but I have my bike pretty well dialed with the stock carb and a JD Racing kit to start fairly easily, within three kicks...as long as I turn the gas tap off when I stop for any length of time, or I'm not trying to do a cold start on a cold day....then the bike can require up to 25 kicks sometimes. I start to wonder if the bike is flooded or the plug is fouled, and on the next kick, the bike roars to life! By then, I'm too tired to ride though.:lol:
 
The compression ratio of a 2 stroke is not like that of a 4 stroke. A 2 stroke by design is similar to a supercharged engine, the transfer ports deliver a pressurized air fuel charge that is timed with an echo effect from the decreasing taper of the exhaust forcing an un-burned air fuel charge back in the combustion chamber from the exhaust pipe. Bigger displacement 2 strokes can't be built with the same mechanical compression ratios and still run on pump gas. You just compared a 250 to a 300 and if you were to look at the average 500 2 stroke and also the other end of the spectrum a 125 you would notice a trend. There is a good bit to be gained by machining the squish band of the cylinder head and using only race fuel if you're looking for more mid-range torque. There is also a point that if you go to far the top end over-rev will suffer and so will the reliability.
 
25 kicks??? wow, thats alot of kicking
Tommy V said:
Ok, crazy idea but will the WR300 start easier with a lower octane fuel? The compression ratio is listed as 6.9:1 which seems really low when you compare it to say, a YZ250 with is around 10.9:1
My YZ ran like crap on anything short of premium with a 20% mix of VP
My WR300 runs great on Shell premium but I'm wondering if the higher octane is actually in part responsible for the finicky starting everyone complains about.
I am running a 36mm Lectron and it's pretty dialed, I always turn the lights off and even in neutral, the bike is a pain in the ass at times. I always make sure to lean on a tree or the side stand so I can stand on the peg and kick but on occasion I will stall it and don't have the option. I can get it started but my knee hurts for a week (torn meniscus) and I. Trying to avoid surgery
I am close to selling the bike for this reason alone. I love it otherwise. Looking for any other tuning tricks to make it fire up easier.
Has anyone tried mid grade or (gasp) even regular in their 300?
Remember, high octane equals slower burn and even less power unless the compression ratio is high enough to match the octane
???
Click to expand...
hard to say, my 360 is even harder to start physically than your 300...still fires to life 2 kicks cold, 1st kick hot. sometimes more after a wreck or something. still starts like this in the winter too, which means 30-35 degrees. lectron 38 running close to 98-100 octane. started the same when it ran 93 octane ethanol, just didnt run as well or consistent.
make sure you run at least premium in your 300, thats not why it isnt starting..
 
Maybe you need to change your technique. I don't run one of them fancy carbs, but if I don't turn on the gas, hit the choke, and lean my 250 over until gas dribbles out of the carb overflow tube, it ain't starting. The guy I bought it from showed me that and he started his 300 the same way.
 
the lectron improved some things for my 360, but it started just as well with the tmx. i had never rode the mikuni in hard core winter situations but it started easily in normal conditions. once i started kicking back instead of down, that is..
 
I was just thinkin this the other day. Not so much for starting, as normally starts pretty easily, more jus for general runnin/tuning/performance. I usually run our 98 but might try the 91 to see if makes any diff.

With the cold start I find if I do it lazy on first attempt(not hard enough n TDC) it mite take 8-10 kicks but if do it properly normally first or second proper kick. Usually first kick wen warm even in gear
 
Using higher octane when it's not needed won't gain any horsepower. Any fuel change usually requires re-tuning. There are advantages to race fuel beyond horsepower gains... a few are no ethanol corrosion, under extreme conditions like overheating the better fuel won't detonate where if you are using fuel that barely meets the requirement and your engine overheats you will likely surpass the marginal fuel and cause damage from detonation, race fuel has a much longer shelf life than pump gas, race fuel doesn't eat away at rubber seals and "O" rings. Personally I use race fuel in every bike, chainsaw, leaf blower 4 wheeler I own. I have found that when used with a full synthetic oil like Amsoil when I tear down my engines they are always carbon free and extremely clean. In the long run I believe it saves me money and I know it saves me time by not having to mess with rotten varnished up fuel.
 
Are you running the stock carb? My bike got easier to start with the PWK carb from JD. I run 100LL AvGas in the winter (To avoid damage from sitting) and it does seem a bit more difficult with that fuel as opposed to 93. But switching from the stock carb to the PWK went from Me almost dieing to get the bike to start for the first time once a week to being slightly winded. But once its warm its never been a problem.
 
I didn't mess with the timing at all, might be worth checking. Overall I think it's just the bad design of the kickstart that gives me the most trouble. If I'm on the pegs with lights off and I find TDC it will fire 2-3 kicks even after sitting a month and one kick after it's warmed up. Sometimes I'm even lucky enough to start it in gear. I was really just wondering if a lower octane would fire a bit quicker and make it even the slightest bit easier to start.
I'm planning on getting a Rekluse for the single purpose of eliminating stalling. I also always wanted to try a LHRB
I'm going to try mid grade for the hell of it next ride to see if there's any difference. At least I might end up saving $2 per ride. Lol
 
As you said the WR300 isn't having a high compression ratio and doesn't need such a high octane fuel IMHO, I have a head with modified squish but same compression and I'm using regular ' pump' 95 octane fuel, over here we use the RON method, the AKI shown in Canada and the United States is 4 to 6 octane numbers lower than elsewhere in the world for the same fuel. Said that, I cannot notice any difference between our 95 and the 98 premium, both are working the same in the bike and starting is also the same (normally first kick with the lectron and kicking from TDC). What I don't like about the fuels here is that they all have about 5% ethanol (E5).

Cheers
 
Important to remember what LankyDoug said, Two stroke CR can not be calculated like 4 Four stroke CR. Its more complicated then that. Ill continue to use 93 to be safe.
 
Tommy V said:
I didn't mess with the timing at all, might be worth checking. Overall I think it's just the bad design of the kickstart that gives me the most trouble. If I'm on the pegs with lights off and I find TDC it will fire 2-3 kicks even after sitting a month and one kick after it's warmed up. Sometimes I'm even lucky enough to start it in gear. I was really just wondering if a lower octane would fire a bit quicker and make it even the slightest bit easier to start.
I'm planning on getting a Rekluse for the single purpose of eliminating stalling. I also always wanted to try a LHRB
I'm going to try mid grade for the hell of it next ride to see if there's any difference. At least I might end up saving $2 per ride. Lol
Click to expand...

I love my Rekluse, great purchase for the WR300 especially if like me you love the tight narrow trails
 
I've been checking out the thread about installing a compression release, seems like a great way to solve my issue. Think I might start there then get a Rekluse.
 
can i ask why you are avoiding meniscus surgery? if you have questions about it, i have had it performed on both knees past few years :thumbsup:
 
Tommy V said:
Overall I think it's just the bad design of the kickstart that gives me the most trouble.
Click to expand...

That's probably most of your issue. I'm 6'3" and fat and starting my 300 has never been an issue. Even when I had the Mikuni and it was way out of whack, it would still start on the first kick. I tore my right MCL while on the trail. My riding buddy that was with me, is about 5'5 and 140lbs soaking wet. As hard as he tried he couldn't start my bike for me. I got on it, let out a painful yell and thankfully it started on the first kick. He just shook his head.
 
Stock carb: Get up front over the bars, put it on top dead center and kick like you mean it directly toward the rear axle and it will start. This is easy if you're 6'6" like me, if not you might have to learn to balance on the pegs like a trials rider. When I had the Mikuni on mine bone cold I had to lean it to the left till it peed out the overflow but after warm it's one kick. Now that the Lectron is on it I can pretty much kick it any way I want and it will start... even in gear with the clutch pulled halfway in it will still start and drag forward on the first kick.
 
Jusitendo, I know Im Gonna have to get it done at some point but it doesn't really bother me unless I tweak it starting my bike or if I'm crouched down and twist the wrong way. I can go months without an issue so it's easy to Forget how painful it is. I also don't want to pay my deductible. Lol. I'm thinking it's cheaper to fix the bike, not to mention that if I get surgery I'm not going to want to risk re injuring it. The less strain on it the better

I'm going to send my head out to Larry Wiechman to have a decomp button installed. It's supposed to then kick over like a 125. Fingers crossed.
I'll report back in a few weeks
 
Seem to remember years ago the dirt bike mags would specify open port compression ratio or closed port compression ratio? Could this be the difference ?
 
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