84 RM250 Fouling plugs - Motorcycle-Journal Forums

stingray_69 · 05-23-2005, 09:06 PM

I just bought an 84 RM250 and it is fouling plugs. I'm new to two strokes so i could use some help. I was running 32:1 and was told to lean it out to 40:1. This did not correct the problem. I know it probably needs to be rejetted but I have some questions before I start with that. First, the exhaust is gummed up. There is oil/gum around where the exhaust exits the cylinder. Is this a problem? Is there anything in the exhaust that I should worry about. I have read somethings on here about power valves but I am not sure what they are, what the do or where the are located. Second, I am assumming before I start with the jetting I should replace the reeds and see what I have. Is this a good idea or do the reeds have nothing to do with plugs fooling. I have check the compression and I am getting and holding 150 lbs so I am assuming this is good enough not to worry about a worn cylinder/rings. How do I know where to start with the jetting? I know I should start with the pilot jet but I have know idea which jet is in there. The bikes stalls when I come to an idle. Is this because the pilot is too rich or too lean. Reving the bike with the clutch in prevents but seems to foul the plug quicker. Lastly, to the Clymer book show a air pilot for the carb but there is not one on there. Is this something specific to the 84?

Dave2122 · 05-23-2005, 10:40 PM

It is normal to get some minor gunk build up around the exhaust headr. With to rich a mixture you willk get quite a lot of sludge buildup around the header and at the end of the silencer. It is hard to give you a step by step on how to jet the bike. I will tell you that your reeds are most likely in good shape if your are holding compression . The carb may have to have the float height adjusted or it may be loaded with dirt or gunk. Also look to see if the needle vlave attached to the float is worn out. Lastly you can jet your bike but i suggest you try and solicite some help from someone with experience doing it. Usually you adjust your main jet and your needle height and once you have that in the ballpark you adjust your pilot etc.....

Here is a rule of thub for jetting and what affect it has on the throttle position and power delivery

Idle circuit/slow jet 0-1/4 throttle
Clip position 1/4 to 3/4 throttle
Needle taper 1/4 to full open throttle
Main Jet 1/4 to full throttle

Hope this helps a little.

stingray_69 · 05-24-2005, 01:31 PM

So you think the reeds are fine? Great! Less to worry about. So the if the bike is stalling at idle and sluggish from 0-1/4 throttle, would this be the pilot?

SuzukiRipper · 05-24-2005, 02:08 PM

its a 2 stroke u gotta rip or else they will stall out there not for crusing

stingray_69 · 05-24-2005, 02:23 PM

It's when I come to a stop or turn I have to pull the clutch in and rev it. Also it will not idle without reving it. Besides Im sure it something in the carb because its a bastard to get started. Lots of time I have to pull the plug and clean it get it started.

SuzukiRipper · 05-24-2005, 04:37 PM

both my 125 and 250 dont idle i dont think they are supposed to

digipoi · 05-24-2005, 08:38 PM

Sounds like it is running rich for sure. What Id do first is give that carb a real good cleaning, soak it in carb cleaner for a couple of days. (You may want to take the time to repack your silencer with some clean packing while you wait). And despite what others may tell you, yes, your 250 can idle.

Go to this site Spanky's Jetting Guide and follow it to the tee. You may have to tweak it a little later when you get comfortable and figure out exactly what your riding style is.

stingray_69 · 05-25-2005, 05:25 PM

Wouldn't repacking the silencer lean it out a bit?

digipoi · 05-26-2005, 02:04 AM

Thats a good question and while I really cant give you an answer for that I can assume that it probably might. Would help with airflow and more air would mean more lean. Still would jet the bike properly to give you the best outcome.

Your previous post says you have problems when coming to a stop or turning so you may want to check your float too.

stingray_69 · 05-26-2005, 06:37 PM

I pulled the silencer off. How does it go throug the packing material. It looks like straight pipe with packing material around the tupe with hole in it. Should there be a baffle or something to force it into the packing?

digipoi · 05-26-2005, 08:40 PM

Usually you have to remove the screws or rivets that holds the canister around the tube. Once you get that off, remove old packing, safety wire new packing around that vented looking pipe thingy, and slide back into housing. The container that holds your replacement packing should give you better details on what to do. At least the Moose brand does.

That tube thats in there is vented usually with little holes or screen around it. Nothing actually gets straight filtered through the fiberglass packing (cigarette style), if you know what I mean. Its just meant to help quiet the noise a little without being too restrictive.

stingray_69 · 05-27-2005, 04:45 AM

Thanks digipoi. I have removed the rivets and pulled it apart. The packing is completely black. I am going to take the silencer to work and clean it out and then repack it.

stingray_69 · 05-27-2005, 09:50 PM

Could the jetting be the cause of the bike starting hard? You have to kick it forever to get it started. Once its warmed up you can get usually get it started within 5 kicks.

stingray_69 · 05-28-2005, 07:35 PM

I went to the Suzuki dealer today and they told me to check what jets it was in it. We only had a book for an 83 and an 85. Since the Clymer book shows the same for an 84 and 85, I told him this and he said the stock jetting should me 300 for the main and 60 for the pilot. I check this against the Clymer book and it shows 320 for the main and 50 for the pilot. What is actually in the bike is 310 and 50. I know nothing about jetting so which would be leaner? I also repacked the silencer and adjusted the float. I adjusted the tab up so this should mean more fuel in the bowl correct. Seems odd but the books said between 10.9 and 11.9 mm, so I adjusted it to 11. When I first fired it up is smoked something terrible and then seemed to settle out to slight smoke. I'll have to run it for a couple of days to see how its doing.

Dave2122 · 05-28-2005, 09:09 PM

The lower the # on the main jet the smaller the opening in it. So the lower # is leaner. Depending on what state of tune the motor is in, and also the elevation and weather conditions will dictate what main jet to use. As an example for an aftermarket pipe would be to lower the main jet to lean out the mix. Same principal for Boyesen reeds.
The more air flowing through the motor the leaner the mixture. You did a good job adjusting the float height! I hope you inspected the needle valve for wear. This valve is what regulates the flow to the float bowl. If it is worn out it will not seal and the float bowl will fill with fuel when it shouldnt and this will cause fouled plugs do to fuel bubbleing up through the main jet.

stingray_69 · 06-19-2005, 07:56 PM

Since the last post, I adjusted the float and the bike went from starting hard to starting up within 3 kicks. Usually on the first. I also swapped out the main to 300 and the bike was smoking quite a bit less. My son had been riding it and it was running great until today. I just quit on him and now it will not start up again. I check the spark and its fine. I checked the air filter is was ok but went ahead and cleaned it any ways. I also took apart the carb and cleaned again just in case the something was clogging the jet. Still nothing. It does not even sound like it wants to start up. It use to kind off back fire if it was kick to many times but not know. I rechecked the compression and I am still getting 150. I have know idea what has happened or what is going on. Can someone please give me an idea of what to do next?????!!!!

Dave2122 · 06-19-2005, 11:48 PM

Even though you have a spark.....Change to a brand new plug of the same #......

One of the first things you learn owning a 2 stroke is.......

Just because the bike is showing a spark doesnt mean the plug is good.

Clean the air filter and a new plug and you should be in good shape.

Also a little tip on 2 stroke pre mix. The cheaper the oil you use the more plugs your going to foul. Cheaper oil needs more of it per gallon and if you are not riding it WFO all the time the cheap oil will build up on the plug and foul it. I use Motul racing premix at 50:1 ratio and have not fouled a plug since 1988 and that is the Gods honest truth.

stingray_69 · 06-20-2005, 04:37 PM

I bought some golden spectro today. It was what the suzuki dealer recommended. He said to mix 40:1. Im really sure that is correct for the oil though. The instructions on the oil are a little veg.

stingray_69 · 06-20-2005, 05:57 PM

Execuse me im not really sure? What do you recommend Dave2122

Dave2122 · 06-20-2005, 09:01 PM

Golden Spectro is perfect at 40:1 and is an excellent oil.

05-23-2005, 09:06 PM	#1 (permalink)
stingray_69 Newbie Joined: May 2005 Posts: 22	84 RM250 Fouling plugs I just bought an 84 RM250 and it is fouling plugs. I'm new to two strokes so i could use some help. I was running 32:1 and was told to lean it out to 40:1. This did not correct the problem. I know it probably needs to be rejetted but I have some questions before I start with that. First, the exhaust is gummed up. There is oil/gum around where the exhaust exits the cylinder. Is this a problem? Is there anything in the exhaust that I should worry about. I have read somethings on here about power valves but I am not sure what they are, what the do or where the are located. Second, I am assumming before I start with the jetting I should replace the reeds and see what I have. Is this a good idea or do the reeds have nothing to do with plugs fooling. I have check the compression and I am getting and holding 150 lbs so I am assuming this is good enough not to worry about a worn cylinder/rings. How do I know where to start with the jetting? I know I should start with the pilot jet but I have know idea which jet is in there. The bikes stalls when I come to an idle. Is this because the pilot is too rich or too lean. Reving the bike with the clutch in prevents but seems to foul the plug quicker. Lastly, to the Clymer book show a air pilot for the carb but there is not one on there. Is this something specific to the 84?

05-24-2005, 08:38 PM	#7 (permalink)
digipoi Seat Tester Joined: Sep 2004 Location: Honolulu Posts: 84	Sounds like it is running rich for sure. What Id do first is give that carb a real good cleaning, soak it in carb cleaner for a couple of days. (You may want to take the time to repack your silencer with some clean packing while you wait). And despite what others may tell you, yes, your 250 can idle. Go to this site Spanky's Jetting Guide and follow it to the tee. You may have to tweak it a little later when you get comfortable and figure out exactly what your riding style is. __________________ 2004 RM250 2004 DRZ125L 2006 TTR-90E 2004 JR50 1993 RM250 1990 KDX200

05-26-2005, 02:04 AM	#9 (permalink)
digipoi Seat Tester Joined: Sep 2004 Location: Honolulu Posts: 84	Thats a good question and while I really cant give you an answer for that I can assume that it probably might. Would help with airflow and more air would mean more lean. Still would jet the bike properly to give you the best outcome. Your previous post says you have problems when coming to a stop or turning so you may want to check your float too. __________________ 2004 RM250 2004 DRZ125L 2006 TTR-90E 2004 JR50 1993 RM250 1990 KDX200

05-26-2005, 08:40 PM	#11 (permalink)
digipoi Seat Tester Joined: Sep 2004 Location: Honolulu Posts: 84	Usually you have to remove the screws or rivets that holds the canister around the tube. Once you get that off, remove old packing, safety wire new packing around that vented looking pipe thingy, and slide back into housing. The container that holds your replacement packing should give you better details on what to do. At least the Moose brand does. That tube thats in there is vented usually with little holes or screen around it. Nothing actually gets straight filtered through the fiberglass packing (cigarette style), if you know what I mean. Its just meant to help quiet the noise a little without being too restrictive. __________________ 2004 RM250 2004 DRZ125L 2006 TTR-90E 2004 JR50 1993 RM250 1990 KDX200

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05-23-2005, 10:40 PM	#2 (permalink)
Dave2122 Sprocket Pilot Joined: Sep 2004 Bike: Which one of the 9? Location: USA Posts: 887	It is normal to get some minor gunk build up around the exhaust headr. With to rich a mixture you willk get quite a lot of sludge buildup around the header and at the end of the silencer. It is hard to give you a step by step on how to jet the bike. I will tell you that your reeds are most likely in good shape if your are holding compression . The carb may have to have the float height adjusted or it may be loaded with dirt or gunk. Also look to see if the needle vlave attached to the float is worn out. Lastly you can jet your bike but i suggest you try and solicite some help from someone with experience doing it. Usually you adjust your main jet and your needle height and once you have that in the ballpark you adjust your pilot etc..... Here is a rule of thub for jetting and what affect it has on the throttle position and power delivery Idle circuit/slow jet 0-1/4 throttle Clip position 1/4 to 3/4 throttle Needle taper 1/4 to full open throttle Main Jet 1/4 to full throttle Hope this helps a little.

05-24-2005, 01:31 PM	#3 (permalink)
stingray_69 Newbie Joined: May 2005 Posts: 22	So you think the reeds are fine? Great! Less to worry about. So the if the bike is stalling at idle and sluggish from 0-1/4 throttle, would this be the pilot?

05-24-2005, 02:08 PM	#4 (permalink)
SuzukiRipper Newbie Joined: May 2005 Posts: 12	its a 2 stroke u gotta rip or else they will stall out there not for crusing

05-24-2005, 02:23 PM	#5 (permalink)
stingray_69 Newbie Joined: May 2005 Posts: 22	It's when I come to a stop or turn I have to pull the clutch in and rev it. Also it will not idle without reving it. Besides Im sure it something in the carb because its a bastard to get started. Lots of time I have to pull the plug and clean it get it started.

05-24-2005, 04:37 PM	#6 (permalink)
SuzukiRipper Newbie Joined: May 2005 Posts: 12	both my 125 and 250 dont idle i dont think they are supposed to

05-25-2005, 05:25 PM	#8 (permalink)
stingray_69 Newbie Joined: May 2005 Posts: 22	Wouldn't repacking the silencer lean it out a bit?

05-26-2005, 06:37 PM	#10 (permalink)
stingray_69 Newbie Joined: May 2005 Posts: 22	I pulled the silencer off. How does it go throug the packing material. It looks like straight pipe with packing material around the tupe with hole in it. Should there be a baffle or something to force it into the packing?

05-27-2005, 04:45 AM	#12 (permalink)
stingray_69 Newbie Joined: May 2005 Posts: 22	Thanks digipoi. I have removed the rivets and pulled it apart. The packing is completely black. I am going to take the silencer to work and clean it out and then repack it.

05-27-2005, 09:50 PM	#13 (permalink)
stingray_69 Newbie Joined: May 2005 Posts: 22	Could the jetting be the cause of the bike starting hard? You have to kick it forever to get it started. Once its warmed up you can get usually get it started within 5 kicks.

05-28-2005, 07:35 PM	#14 (permalink)
stingray_69 Newbie Joined: May 2005 Posts: 22	I went to the Suzuki dealer today and they told me to check what jets it was in it. We only had a book for an 83 and an 85. Since the Clymer book shows the same for an 84 and 85, I told him this and he said the stock jetting should me 300 for the main and 60 for the pilot. I check this against the Clymer book and it shows 320 for the main and 50 for the pilot. What is actually in the bike is 310 and 50. I know nothing about jetting so which would be leaner? I also repacked the silencer and adjusted the float. I adjusted the tab up so this should mean more fuel in the bowl correct. Seems odd but the books said between 10.9 and 11.9 mm, so I adjusted it to 11. When I first fired it up is smoked something terrible and then seemed to settle out to slight smoke. I'll have to run it for a couple of days to see how its doing.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

05-28-2005, 09:09 PM	#15 (permalink)
Dave2122 Sprocket Pilot Joined: Sep 2004 Bike: Which one of the 9? Location: USA Posts: 887	The lower the # on the main jet the smaller the opening in it. So the lower # is leaner. Depending on what state of tune the motor is in, and also the elevation and weather conditions will dictate what main jet to use. As an example for an aftermarket pipe would be to lower the main jet to lean out the mix. Same principal for Boyesen reeds. The more air flowing through the motor the leaner the mixture. You did a good job adjusting the float height! I hope you inspected the needle valve for wear. This valve is what regulates the flow to the float bowl. If it is worn out it will not seal and the float bowl will fill with fuel when it shouldnt and this will cause fouled plugs do to fuel bubbleing up through the main jet.

06-19-2005, 07:56 PM	#16 (permalink)
stingray_69 Newbie Joined: May 2005 Posts: 22	Since the last post, I adjusted the float and the bike went from starting hard to starting up within 3 kicks. Usually on the first. I also swapped out the main to 300 and the bike was smoking quite a bit less. My son had been riding it and it was running great until today. I just quit on him and now it will not start up again. I check the spark and its fine. I checked the air filter is was ok but went ahead and cleaned it any ways. I also took apart the carb and cleaned again just in case the something was clogging the jet. Still nothing. It does not even sound like it wants to start up. It use to kind off back fire if it was kick to many times but not know. I rechecked the compression and I am still getting 150. I have know idea what has happened or what is going on. Can someone please give me an idea of what to do next?????!!!!

06-19-2005, 11:48 PM	#17 (permalink)
Dave2122 Sprocket Pilot Joined: Sep 2004 Bike: Which one of the 9? Location: USA Posts: 887	Even though you have a spark.....Change to a brand new plug of the same #...... One of the first things you learn owning a 2 stroke is....... Just because the bike is showing a spark doesnt mean the plug is good. Clean the air filter and a new plug and you should be in good shape. Also a little tip on 2 stroke pre mix. The cheaper the oil you use the more plugs your going to foul. Cheaper oil needs more of it per gallon and if you are not riding it WFO all the time the cheap oil will build up on the plug and foul it. I use Motul racing premix at 50:1 ratio and have not fouled a plug since 1988 and that is the Gods honest truth.

06-20-2005, 04:37 PM	#18 (permalink)
stingray_69 Newbie Joined: May 2005 Posts: 22	I bought some golden spectro today. It was what the suzuki dealer recommended. He said to mix 40:1. Im really sure that is correct for the oil though. The instructions on the oil are a little veg.

06-20-2005, 05:57 PM	#19 (permalink)
stingray_69 Newbie Joined: May 2005 Posts: 22	Execuse me im not really sure? What do you recommend Dave2122

06-20-2005, 09:01 PM	#20 (permalink)
Dave2122 Sprocket Pilot Joined: Sep 2004 Bike: Which one of the 9? Location: USA Posts: 887	Golden Spectro is perfect at 40:1 and is an excellent oil.