Mikuni BSR36 carb on a DRZ400E

[JTorres]

I recently purchased a 2004 suzuki DRZ 400E that came with the carb Mikuni BSR36 carb. It had been running rich, but still running for a while. I am wondering if there are any recommendations on jetting this carb properly for the E model. I am not sure if the hot cams and higher compression require different jetting or not. Either way. The bike was running, now she wont fire. I have ruled out the stater, battery, spark plug. Only thing left is the fuel/ air system. I had recently pulled and cleaned  the carb and she was running great for weeks. When I pulled the spark and tested it, it was back and sooty. (Bikes running rich)

Any suggestions?

[ctrials]

You need to check the valve clearances first so you're not chasing your tail.  A classic symptom of valves being out of spec is the bike is hard to start.

[ptgarcia]

Need more information. What is the current jetting in the carb? What are typical temperatures and elevations you ride in?

[shuswap1]

Does the oil smell like gas? Hidden and easily overlooked O-ring located just under the float valve seat is a common culprit. Leaking at that location can cause hydrolocking, thinned oil and shite running, ask me how I know!

Edited February 3, 2020 by shuswap1

[38super]

https://docs.google.com/spreadsheets/d/1HNSB3DrqJqHTInjVDKKS4HNSHZPbdK0ElbfNI5HxuZg/edit#gid=1132379936

[JTorres]

We took the top end of the motor apart and checked valve clearances. They were within spec. I went through the carb and rebuilt it. She ran fine for months. Then began to die at idle. I thought it was an electrical issue. My old lead acid may still be the culprit. I have my friends brand new lithium battery from his DRZ400. Upon fixing some faulty wiring on my headlight assembly, all electrical issues seem to be ruled out.

My oil does smell like gas, and the last time the bike fired up and ran on choke at high rpm, my radiator overflow started spewing steaming coolant.

I have the mikuni BSR36 (29FB)

142.5 main jet

22.5 pilot

The fuel screw is an aftermarket extended one that I can adjust on the fly. I had trouble getting the bike to run well with it more than one full turn out.

I reside in Austin Tx and that is where we have been riding. However, we will be hauling these bikes up to grand junction and moab. So i know im gonna have to re jet for that. Just want to be able to rip it here in texas for the time being.

[shuswap1]

BSR is pretty forgiving re jetting. And the jets you're using worked fine in my BSR....I ride from sea level to 8,000' and don't change anything. I did use the DJ needle and spring, which really helped.

If the oil smells at all of gas then 98% certainly you have the o-ring issue. Can we assume it wasn't changed when you last rebuilt the carb ? It is easy to overlook and would account for the running issues you describe.

Edited February 3, 2020 by shuswap1

[JTorres]

I changed the o ring on the needle valve seat, but not the valve seat it self. The part seemed to be in well enough condition to keep in the carb. However, I think you are right. I have a replacement valve seat and will be reinstalling this evening. Beyond this though, are there any other reasons gas would leak into my oil system?

On a separate note, would anyone have any recommendations for jetting this mikuni caburator for the 04' DRZ400E

Even when the bike was running, my fuel screw was less than one turn out to get it to run proper and my idle adjust was less than one full turn out.

Thank you all for all the imput. Much appreciated.

[shuswap1]

Pretty rare for the needle to need replacing they seem to be of stellar quality.

Fuel seeping into the oil will enrichen the mixture the engine receives, so best to fix that before trying the jetting. Is the float level correct? I'm surprised the needle seat o-ring is not the source of your fuel-in-oil issue. Do you have a manual petcock?

[JTorres]

The float level is within spec for this carb. 13mm. I checked it when I pulled the carb apart yesterday. I also made sure the float itself was not compromised. It has not been punctured or eroded to the point it would take on fuel. I have replaced the brass valve seat and placed a brand new o ring on it. I am also going to change the oil and re clean the carb. I have a feeling the valve seat might be the root of my problem.

Would the enriched mixture cause my engine to run hot enough to cause coolant to steam out the radiator overflow hose?

[roleyrev]

43 minutes ago, JTorres said:

The float level is within spec for this carb. 13mm. I checked it when I pulled the carb apart yesterday. I also made sure the float itself was not compromised. It has not been punctured or eroded to the point it would take on fuel. I have replaced the brass valve seat and placed a brand new o ring on it. I am also going to change the oil and re clean the carb. I have a feeling the valve seat might be the root of my problem.

Would the enriched mixture cause my engine to run hot enough to cause coolant to steam out the radiator overflow hose?

Letting the bike idle for extended time will cause this to happen. The DRZ E model (that I know) doesn't have a radiator fan and relies on flow of air (from riding) to keep cool.  You may have a different setup as E models that I have come across have the FCR39 and not the BSR36.

[shuswap1]

Manual petcock? On-Off-Reserve? They get hot idling-no air flow through the radiators.

Edited February 4, 2020 by shuswap1

[JTorres]

My petcock stays on. It has on, reserve, and a prime(which just dumps fuel). I have always started the bike with the petcock in the on position. Never have had to prime. Though I did try it once when trying to troubleshoot the bike after it wouldn't start.

[shuswap1]

That model petcock can still flood the engine, I think. Might be through the vac hose? Shite memory, I switched out to a manual petcock several years back!

Have a look here:

https://thumpertalk.com/forums/topic/877487-drz-400-s-petcock-fix-cheap-easy/

Edited February 4, 2020 by shuswap1

[JTorres]

Thanks. I will have a look at the linked topic, do some wrenching and get back with any updates.

[JTorres]

I know we had some responses on possible

On 2/3/2020 at 6:33 PM, roleyrev said:

Letting the bike idle for extended time will cause this to happen. The DRZ E model (that I know) doesn't have a radiator fan and relies on flow of air (from riding) to keep cool.  You may have a different setup as E models that I have come across have the FCR39 and not the BSR36.

My E model had come stock with the FCR39. It got swapped for the BSR36 that came off of an S model of the same year. The bike had been running super rich. I am wondering if I need to downsize my main jet. Any thoughts?

[shuswap1]

1 hour ago, JTorres said:

I know we had some responses on possible

My E model had come stock with the FCR39. It got swapped for the BSR36 that came off of an S model of the same year. The bike had been running super rich. I am wondering if I need to downsize my main jet. Any thoughts?

That's the stock 142.5 I ran in my BSR, worked great. I'm sorry to say that if the oil smells of gas you need to find and deal with that issue before messing with jetting that we all know works just fine elsewhere. Are you quite certain the oil smells of gas?

[dookiller]

If you got coolant spewing out you have head gasket issues. That will make it hard to start as well. From continually trying to start it with lack of compression and raw fuel entering the combustion chamber you may get fuel in the oil. Do a compression test to ensure head gasket is fine. I aint no mechanic but know if your overflow is puking out water once started you have compression leaking into your coolant. Take rad cap off and crank it or start it if possible. If it's bubbling there is your probl;em.

[JTorres]

On 2/8/2020 at 12:31 PM, shuswap1 said:

That's the stock 142.5 I ran in my BSR, worked great. I'm sorry to say that if the oil smells of gas you need to find and deal with that issue before messing with jetting that we all know works just fine elsewhere. Are you quite certain the oil smells of gas?

I am positive the oil smells of gas. I found and replaced the valve seat and o ring where the torpedo sits in the carb. I havent had time to put it all back together and see what happens. Would you recommend replacing the oil before I put everything back together and trying to start her again?

22 hours ago, dookiller said:

If you got coolant spewing out you have head gasket issues. That will make it hard to start as well. From continually trying to start it with lack of compression and raw fuel entering the combustion chamber you may get fuel in the oil. Do a compression test to ensure head gasket is fine. I aint no mechanic but know if your overflow is puking out water once started you have compression leaking into your coolant. Take rad cap off and crank it or start it if possible. If it's bubbling there is your probl;em.

I will look into this.

[shuswap1]

3 hours ago, JTorres said:

I am positive the oil smells of gas. I found and replaced the valve seat and o ring where the torpedo sits in the carb. I havent had time to put it all back together and see what happens. Would you recommend replacing the oil before I put everything back together and trying to start her again?

I will look into this.

Not sure what you are referring to when you say 'torpedo'?

The o-ring is under the removable seat that the rubber-tipped float needle valve pushes against.

Oil that is contaminated with gas has much reduced lubrication qualities, so yes, it should be drained before running the engine. In the days of old they used to thin straight-weight oils with gas when the temps were far below freezing, just so they could get the thing to start. But those engines had very short lives in comparison. Change the oil !

Edited February 10, 2020 by shuswap1