Here's my problem: My sons 03 LT 50 has ran with no problems for the past two months and all of a sudden last week it struggled to start. Eventually it kicked in but felt rough. I picked up new plugs but they differ a little from the manual. The manual lists BPR-4H, but all that is available is the BPR-4HS, so I picked them up. Even looking at the NGK homepage they listed the BPR-4HS for the LT 50 I have.

Anyway, I decided to replace the plug that was in the quad (we got the quad used). The plug in the quad was either a BR-4h or a BP-4H. In looking at it the main difference (between the BPR-4HS and BR-4H) was the length of the tip, actually a good size difference (BPR-4HS was longer). The BR-4H was the plug that was in the quad when it ran fine and then after about the four short rides started giving me problems starting. So I put in the BPR-4HS and it started right up. Happy, I put the quad away for another day. Well, today I went out and tried to start it and it absolutely refused to catch. I triple check the obvious stuff and nothing. I even put the old plug back in to see if I was missing something important, but the same thing...nothing. The only thing to note is I had the carb on PRI to get the initial start up. When I did this and pulled the cord a couple times, I had a good size gas puddle underneath. Did I just completely flood this thing that it would show no signs of starting?

My next step is to pull all the plastics off to see if there's something obvious, but I though I'd throw this out to see if anyone has recommendations.

Thanks in advance for any advice.

 

I had the exact same problem this weekend with my son's new (to us) 2002 50. It has a BPR-4HS plug in it, that fouled and wouldn't start. We also got the same puddle of gas from the carb vent tube. I'm thinking the float might be stuck???

 

As I mentioned the NGK site lists the BPR-4HS as the proper plug, so I'm thinking that wasn't the problem. Today I went out there and just stared at, gave it a couple tugs and thought I'd check the carb. Wow, I pulled the drain screw and vast amounts of fuel flowed out. I closed it back up and after a couple tugs she fired up. Now, when I shut it down after taking my own spin around the yard, the same thing happened. Before it would start I had to drain the carb again.

I'll keep toying with it, but for now I'm just happy to figure out what the problem was. Please add updates as you progress with yours.

If anyone can think of some advise, I'm not against constructive feedback. Thanks.

 

Pri is short for prime. This allows a gravity feed of gas to flow. Sometimes if the needle and seat have a bit of debri, sand ,paint chip, hair, etc. holding it open the PRIME position may load the engine with fuel.
I think your Bp4hs plug is fine , along with a B4hs.