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Hello all,

Here is the story, I just bought a 06 ltr450 with a big bore kit, open air box, gutted exhaust and yoshi cherry bomb. Just out of the shop. I have taken this quad out about 4 times now. The symtoms are as follows, when I first start it it runs great for about 20 mins or so. Full power and fun, but after that it looses 90% of power and I can barely make it back.

First trip, having fun riding around, after about 30 mins or so, i hit the throttle and it get barely any power. It almost feels like when an engine goes into limp mode. I turn off and restart, still same. Also its hard to restart. I notice there is a inline fuel filter going to the pump, i hit it couple of times and the engine gets little more power. So I am thinking bad filter.

second trip, so I change out the inline fuel filter to a different one and go out. Same results as the first trip, ok for about 20 mins then same problem.

Third trip, I do a lot of reading and decided that maybe the fuel pump is on its way out and change it out. After I changed it, it felt like I gained 5 more hp! I was confident that fixed it

Fourth trip, SAME FREAKING THING. Runs great for about 20mins and starts to bogg again.... I decided to take off the cherry bomb, Nope the problem is still there. I don't know what to do anymore. I really don't want to take it to the dealer. Alot of the post that I read was bogging from the beginning, mine is doing it after it rides great for about 20 to 30 mins. Please help!!!
Also, anyone recommend a good shop in Southern CA? Zip code 91748?

Thank you for all the help
 

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Dpeending on how big your big bore is, you may need a programmer and tune. but as far as your current problem, you need to start by testing your fuel pressure. I Would test it cold and then test it when its hot and acting up.
 

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If you bought one of those cheap fuel off ebay that may lead to the same problem as well.

I bought the honda fuel pump per forum discussion from amazon. As soon as I put it in and took her for a spin, it felt at least 5 hp stronger.

Dpeending on how big your big bore is, you may need a programmer and tune. but as far as your current problem, you need to start by testing your fuel pressure. I Would test it cold and then test it when its hot and acting up.
Well, I was thinking , if I needed a programmer and a tune, wouldn't the problem start from the beginning? I mean the quad rips for about 20 mins, then thats when it starts to go into some type of limp mode or no power.

Thats where I was leaning to next. I guess I will have to bring a fuel gauge with me next time I ride and see. I am also just going to get new plugs put in and see as well.
 

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Discussion Starter #5 (Edited)
So I followed the manual 5-5 and did the fuel pressure test at my house. Here are the results

As soon as switched on, I can hear the New pump prime and it goes to 50PSI and starts to lose pressure. It does it gradually, it takes good 10 to 15 secs before getting down past 30. It doesn't hold the pressure at all. It starts to loose pressure, keeps going down past 30psi. Tried it 3 times with same results.

I actually started the engine, starts fine, it stays at 50 psi the whole time its running, idle or being reved same. 50PSI.

This is done in cold start condition when the quad runs great. I have to take the quad out to run it, can't do it in my neighborhood, so I can't test when bogging yet.

Is it possible that the FPR works somewhat ok when its been sitting for a while, then as fuel is being pushed through( like running for 20 mins or so) cause the FPR to loose more pressure in the diaphram or spring and makes my quad run bad?

Is this normal?

Thank you!
 

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I've heard of a lot of unsuccessful attempts to clean FPR's.
Ok. But would the bad fpr can cause my symtoms? It only runs bad after riding for a bit.
If it's bypassing too much fuel and allowing the pressure to drop below spec, it's possible. You should probably verify the psi when it's acting up to see.
 

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Discussion Starter #11
I've heard of a lot of unsuccessful attempts to clean FPR's.
Ok. But would the bad fpr can cause my symtoms? It only runs bad after riding for a bit.
If it's bypassing too much fuel and allowing the pressure to drop below spec, it's possible. You should probably verify the psi when it's acting up to see.
I really appreciate your help. At this point, regardless the pressure is too high so I am going to change it out. I will report back next time I taker her out. I will make sure I bring the fuel guage with me to measure when its acting up.
Thanks
 

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Discussion Starter #12
Just picked up the FPR from dealership who price matched online price!!! Going to put it in and test pressure. Wish me luck!
 

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I am happy to report that my problem has been solved.

Here is the weird thing that happened. After I finished with all the repairs, the bike fired up and took it out for a quick spin. It was running fine for like 2 mins, then the bike just dies and wouldn't crank or prime. So I checked the battery and it was dead. I charged it over night and it wouldn't charge. I replaced the battery and started right up. I didn't know batteries dies instantly like that.
Here are the things that I did in combination. I don't know which one exactly solved the problem, but i think the fpr was the culprit.

Replaced FRP now reading 42 PSI.
Bypassed the Swirl Filter
Installed new Glass inline 100micron fuel filter
Replaced spart plug with new E style spark plug.

After all repairs, put new battery in it.

Took it to El MIrage yesterday and ran it for 3 hours with no problems what so ever. I never realized my quad had this much power LOL.

Another note, I had 5th gear pegged and all I could get was 65MPH using my gps. Is this normal with my mods? Thank you for all of your help!

Kalvin
 

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Discussion Starter #15

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That's why I posted the gear ratio calculator.

Im running a 3.0 gear ration on 20" tires. It is geared lower than most.
 
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