DRZ DRZ400s lean running

[LeadHead]

Hey DBA! It's been awhile!

Long story short, I have been building this shitty DRZ on a budget. Bought it cheap without a title, swapped the frame, and now I'm here!

I cleaned the carb twice. I noticed the jets are pretty rich at a 30 pilot and I think a 162.5 main. Most people with my mods (3x3, FMF muffler) are running 22.5 or 25 and around 145-150. I suspect there is an air leak somewhere but I can't find it by letting it idle and spraying starting fluid around the boots. I also taped up the 3x3 hole to about 1X2 and not much change.

Any ideas that I may be over looking?

 

[Mihylo33]

Hey DBA! It's been awhile!

Long story short, I have been building this shitty DRZ on a budget. Bought it cheap without a title, swapped the frame, and now I'm here!

I cleaned the carb twice. I noticed the jets are pretty rich at a 30 pilot and I think a 162.5 main. Most people with my mods (3x3, FMF muffler) are running 22.5 or 25 and around 145-150. I suspect there is an air leak somewhere but I can't find it by letting it idle and spraying starting fluid around the boots. I also taped up the 3x3 hole to about 1X2 and not much change.

Any ideas that I may be over looking?

Sell that bike for diaper money!
What happens when you lean the bike out?
What year is it?
Did you know fmf doesn't have carb specs but they will send you a jetting kit?

 

[2strokesteve89]

Hey DBA! It's been awhile!

Long story short, I have been building this shitty DRZ on a budget. Bought it cheap without a title, swapped the frame, and now I'm here!

I cleaned the carb twice. I noticed the jets are pretty rich at a 30 pilot and I think a 162.5 main. Most people with my mods (3x3, FMF muffler) are running 22.5 or 25 and around 145-150. I suspect there is an air leak somewhere but I can't find it by letting it idle and spraying starting fluid around the boots. I also taped up the 3x3 hole to about 1X2 and not much change.

Any ideas that I may be over looking?

Is it lean at idle or cruise? Unless it runs lean at idle, your air leak test won't work.

 

[LeadHead]

Sell that bike for diaper money!
What happens when you lean the bike out?
What year is it?
Did you know fmf doesn't have carb specs but they will send you a jetting kit?

I might have to if she keeps giving me trouble!

I haven't been able to mess with the fuel/air screw because the Mikuni has a plug over it that I have to drill out. When I cover the air box hole, it seems to idle better, but still pops as it comes back down in rpm.

Is it lean at idle or cruise? Unless it runs lean at idle, your air leak test won't work.

It used to bog out and stall pretty bad. It's gotten better I think. It's kind of unpredictable. Perhaps closing the air box hole has made it slightly better.

Both the pilot and main are pretty rich sizes as is, but is still running lean

 

[Mihylo33]

You have an air leak. Head gasket, carb boot untreated air filter ..... float set and did you clean the carb 3 times?

 

[MikeinFresno]

you start by saying the jets are rich then you cover the air box holes which should make it more rich again. Take air box side cover off and try it-this will lean it out some

 

[LeadHead]

you start by saying the jets are rich then you cover the air box holes which should make it more rich again. Take air box side cover off and try it-this will lean it out some

I probably didn't explain well enough. The jets installed are rich compared to the jets commonly installed for the same mods. 30 pilot when people typically use 22.5 or 25. 165 when people typically use 145-150.

However, my bike is acting as if it is running lean.

You have an air leak. Head gasket, carb boot untreated air filter ..... float set and did you clean the carb 3 times?

I cleaned the carb twice so far. The air filter is brand new also.

The head gasket...is there any indicators or tests to rule that one out? The oil looks fine as far as coolant leaking.

I guess I'll try the starting fluid thing again. Any other ideas on figuring this out?

 

[Mihylo33]

I probably didn't explain well enough. The jets installed are rich compared to the jets commonly installed for the same mods. 30 pilot when people typically use 22.5 or 25. 165 when people typically use 145-150.

However, my bike is acting as if it is running lean.



I cleaned the carb twice so far. The air filter is brand new also.

The head gasket...is there any indicators or tests to rule that one out? The oil looks fine as far as coolant leaking.

I guess I'll try the starting fluid thing again. Any other ideas on figuring this out?

It's quite possible that there is raw fuel dumping into the exhaust. That will create a popping.

 

[Trfsrfr]

but still pops as it comes back down in rpm.

Not sure what carb you have or if it even has one of these since you haven't mentioned what year it is, but my klx650 has a vacuum slide carb and it has an air-cut valve/rubber diaphragm thingy on the side of it about 1-1/8" diameter that is supposed to richen the mixture when you back off the throttle to keep it from popping. I had to replace mine and they arent cheap. Looks like #43028 in the photo below.
Might be worth looking into for the popping issue...

 

[MikeinFresno]

popping also can be due to an air leak in the exhaust system...the leak causes air to be sucked in on decal and the added oxygen then ignites the unburned fuel in the pipe. This is common on a KTM where there is no positive seal at the head or joints. Most street legal bikes have a good gasket/bolt on system so they usually wont leak air. But if an after market pipe was added it may be the cause.

Also, you say it is acting as tho it is running lean...what exactly is it doing that makes you think this-especially since it is jetted rich?

 

[Trfsrfr]

Lets see a photo of the spark plug...