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SixStrings12

2002 Foreman 450 - MBRP Aftermarket Exhaust - Lost top end?

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So, after the insides of my stock exhaust on 2002 foreman 450s let go and started rattling, I purchased an MPRB slip on after market exhaust and installed it a few weeks ago...

Let's just forget about the "slip-on" bit - I had to take it to an exhaust shop and get the inlet enlarged by 0.05 of an inch to get it to "slip-on" to header pipe..

Then the mounting instructions were completely wrong...said to discard the OEM spacers - ahh..no...you either use the spacers or have to invert the mounting tabs to get it to clear the shock...

Then it had an air leak at the exhaust to inlet pipe connection - all they tell you to do is slip the pieces together and use a supplied spring to keep the exhaust and inlet pipe together...ahh, again, no...you need to buy some Exhaust goop and ensure that connection is air tight.

So, after all that nonsense, I take it out for a test ride...

Bottom end power is fine...actually feels like a little more grunt..but I lost at least 10 km/h on my top end...I could hit 60 km/h no problem with the stock exhaust, now I am lucky to hit 49 km/h. FYI, I do have 26" zillas on this thing, so I know that saps some top speed from stocker tires, but still...

You can hear the motor winding out, but it simply does not get back up to top speed any longer...

Before I check the spark plug, anyone else experience something like this with an aftermarket exhaust?

Yes, I will eventually cut open the stocker and repair it, but wanted to get this thing going asap and bought the MBRP exhaust...

Thanks for any insight.

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So did it do 60 KM/H with the 26's on it, with the only difference at all in 60 KM/H and 50 KM/H being the changed exhaust?

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So did it do 60 KM/H with the 26's on it, with the only difference at all in 60 KM/H and 50 KM/H being the changed exhaust?

 

Yes, only change was the exhaust.

 

  Thanks

 

Edited by SixStrings12
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Sounds like either the new exhaust doesn't have as much flow as stock, or it might have more flow which means your jetting is now off.

 

Have a link to the muffler you put on?

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Is this what you installed  ??  Would think it is more restrictive to the flow since you lost --- Honda made a 450 Sport ATV , maybe this muffler is for it , since you mention it was suppose  to use a spring to hold the muffler on , like a Sport ATV does  ---- maybe your old muffler was worn out giving you more performance , LOL 

 

$194.99 BRMP Honda ATV Direct Replacement Slip-On with Utility Muffler #7105 

image.png

  

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Given the only review on there says it bolted right on and was a perfect fit, and it says "improved flow" and "no tuning required"

 

Given what all you had to do, I wonder if you didn't get the wrong part.......

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2 hours ago, Fishfiles said:

Is this what you installed  ??  Would think it is more restrictive to the flow since you lost --- Honda made a 450 Sport ATV , maybe this muffler is for it , since you mention it was suppose  to use a spring to hold the muffler on , like a Sport ATV does  ---- maybe your old muffler was worn out giving you more performance , LOL 

 

$194.99 BRMP Honda ATV Direct Replacement Slip-On with Utility Muffler #7105 

image.png

   

    Yes, this thought crossed my mind as well...  So, obvious next step is to do a plug chop, but I have asked this before on other forums and just got 'crickets'...

 

  How do you do a plug chop on a semi-auto transmission ATV?   You are supposed to go balls out in 5th gear and cut the engine, then inspect the plug - how do you do that on a semi-auto machine and not destroy it?

 

 Thanks for the replies everyone - much better site than "the other one"...

 

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So what you calling the other site ? HondaAtv ?? 

 

I have a 2002 450 with a stock muffler , boy , that muffler is  expensive if you were to ever have to buy one , they were  over $1,100 without the heat shield ,  that muffler is no longer available from Honda , but I do see one looks exactly like stock for around $300 on e-bay , probaly Caltric  ---  also have a 2000 with a HMF muffler , that one screams and is very loud , but  will only do 19mph with a 20 mph wind at my back , LOL , it has 34.5% gear reduction with 29.5s 

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18 hours ago, SixStrings12 said:

    Yes, this thought crossed my mind as well...  So, obvious next step is to do a plug chop, but I have asked this before on other forums and just got 'crickets'...

 

  How do you do a plug chop on a semi-auto transmission ATV?   You are supposed to go balls out in 5th gear and cut the engine, then inspect the plug - how do you do that on a semi-auto machine and not destroy it?

 

 Thanks for the replies everyone - much better site than "the other one"...

 

 

I think the next step for me would be to call the muffler seller and confirm that you got the right part. 

 

Of course, now that you've "tweaked" it they might not be willing to do anything, but won't hurt to call them and confirm that you got the right part.

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