So I've been reading all summer on the 351 kit from Blue I really want this for my SF I figure by Dec. the weather might become too bad to ride so that is my time to do it. But I got to thinking. 95% of my read his be people talking about the kit on their S models and how great it is off road. So I got to thinking how the kit is on the street does anyone have a good report on street use for the 351 how does it hold up to long periods of high RPM's like cruising 75 mph etc? Also those of you that made the switch did you switch carbs as well?

Thanks guys!

 

In for a answer curious aswell!!!

 

Yeah in for answers as well.

After I get the suspension right I want to get as much (reliable) power as I can.

 

I'll chime in with my opine. I got an 06 with lots of hard miles. First I put in a klx 300 piston....about a year ago I put in the 351 kit.

Part of my run to riding consists of 70-75 mph thumping on I95 for about 40 minutes each way.....no issues at all.

If its dark out thou you will notice your Muzzy header glowing..lol. Vibes are also not an issue, but as a disclaimer my other bike is a ktm 640 with an lc4.

 

how is the power? Havde you ever had any overheating issues?

 

So how would you compare the 250 to 300 to 350?

I'm considering a 300 piston, and barrell, but it may turn out that not a lot more money will get me the 350.
Decisions, decisions.

 

There's a very noticeable bump going to the 300, and while I haven't ridden a 351, I can't imagine that there's not a very noticeable bump there too. The old saying, "there's no replacement for displacement" has some merit. That said, after doing my 300 kit and seeing the valve reliefs on the 250 piston, I wonder if there's an inherent inefficiency to the 250 engine. Historically if I understand correctly, the 250 came before the 300 internationally. However, the 300 head's valve placement looks like it was designed for the 300 specifically. When the '06 250 came out, they had to put the valve reliefs in the piston crown extending down over the edge of the piston. I'm thinking this is not the ideal valve-to-piston design, but then I'm not an engineer. The valve relief locations on the 300 piston look like the "normal" position in modern 4-strokes. I'd be curious to know if the original 250 piston has the same valve relief location as the '06 and later 250 piston. It would also be good to know if the original 250 has the same head as the current 250. The current 250 uses the same head as the 300.

 

Hi there,

I purchase 351 kit for my 09 sf in the spring, very nice man Bill Blue and i spent most of the summer trying to tune my carb CVK. 1 month ago i purchase BB tm34 carb put it on and it is right on the money best move i made.. i have 15 tooth front gear and i pull the front wheel in 2 gear with trottle only nice ride ..

 

Installed 351 about 600miles ago. Also, installed 36mm carb from Bill Blue. Great guy. I ride around town, on local freeways and off road. No over heating, pulls hard at 75, need a 15 front or 40 rear sprocket. 1st gear is useless off road and it should pull taller highway gearing easily. I couldn't be happier

 

Good question, I'll try to provide my opine ...... BUT I am not going to be drawn into an argument about it.

The install of a klx 300 jug led to a good performance gain....say 15%......which was really good and made the bike usable in sugar sand, but just barely. Overall the 300 bump over the 250 really made a fair improvement.....ask EMS our hotd poster.....he has ridden my klx 300.

Bumping up to the 351 kit was ..... well a little disappointing....torque was up and it was better hp wise.....but not as much as it should have been, I think the head was restricting the large air flow.

Soooo.....I had the head ported, 101 cams and slightly larger valves......and WOW.....solid 30 hp I bet.

Just sayin.