Hello All,

First off, I’m new here but loving the fact this site exists! I am not too new to the ATV world but I would say I am borderline still a Rookie (about 2 years under my belt). With that being said, I have been trying to learn as much about ATV's as I can so that I am able to be knowledgeable and work on them myself.

Anyway, here is my question: Last year I installed a DG Performance on my Honda 400 ex. Just this week, I installed a "silencer" on it (from DG Performance) to quite it down slightly as we are on a trip in WI and they have decibel laws on the trails we are on.

Now My 400 won't run without the choke being on. I can't figure out if that has to do with my modifying the exhaust or is a coincidence and is entirely unrelated...maybe the carbs need cleaning? the machine was ridden the week prior without the exhaust silencer and ran just fine though....

Any help would be EXTREMELY appreciated, thank you so much for any help.

 

When you install a performance pipe and silencer, you are allowing the exhaust to flow more freely. This results in a lean condition. You are going to need to go larger on you main jet. If you give info regarding where you live, elevation, any additional mods, etc., someone with a similar set up can tell you what they are running. DG should be able to give you a ball park guess on what main to run. Buy a few extra OEM jets once you have a base line so you can dial it in just right.

 

ok, thanks for the information. I am still confused though to be honest, I get the concept of installing the aftermarket exhaust and it being able to flow more freely. But the silencer actually makes the hole smaller, so does that not restrict the airflow?

So since I didn't have issues with the DG exhaust until after the silencer was installed could it be the opposite affect? Not enough air flow? Although I guess I am not sure how the choke would fix that..

Thanks for the help/clarification & recommendation. I life in Minnesota (about 2,000 feet elevation). Its mostly a flat state other than some bluffs. I have heard about re-jetting the carb, so especially after your advice I will have to do that.

 

Clean the carb out. You can check jet sizes while you are doing it, and put a bigger main jet in if the bike still won't run without choke after cleaning.

 

 

If it was running fine before changing your exhaust, there is a very good chance that that is the issue. By running the choke, you are creating a rich mixture and if it runs fine when you do this, it does appear to be running lean. Take a look at your spark plug. The color will help give you an indication of your fuel mixture. Also check your air filter and make sure it is clean. Like merryman said, clean the carb thoroughly. It definitely can't hurt. Contact DG and tell them your setup. Like I said, they will be able to give you base line to work with and hopefully someone from this forum has a similar setup at your elevation that can chime in.

 

Thank you for the advice.


Thanks

Ok, thanks for all your advice!