Jump to content
Sign in to follow this  

Sluggish throttle response on RM85

Recommended Posts

I would greatly appreciate any help given. My son has an 08 RM85, and we rode over the weekend, and I noticed that is had lost a little snap. The bike has less than 20 hours on it. I just replaced the spark plug, because it is also fouling plugs. I ran a 30:1 ratio during break-in, and it fouled 5 plugs, before I increased the ratio to 32:1. We got a little more life out of the plugs then. Anyway, it always had good snap. I could roll the throttle hard, and it would instantly be wide open. Now its taking a little while ( not long, but noticeable) to rev into the powerband. The gas I have is a few months old, due inability to ride, because of the "lowcountry" heat, and little league baseball. Any thoughts, suggestions? Could the gas be old? Again, I would greatly appreciate any help!!!

Share this post


Link to post
Share on other sites

Switching from 30:1 to 32:1 would normally make the fouling WORSE as you increased the fuel percentage and decreased the oil percentage.

99% of the time, fouling plugs is due to having too much fuel and has nothing to do with oil.

In this case I think you have bad gas.

ANY pump gas that is MONTHS old, no matter how it is stored is JUNK !

The only fuel that is really stable for months is aviation gasoline AV100LL which MUST, by US federal law, be octane and content stable for two full years if stored properly. Leaded Racing fuel is usually stable for about 6 months if stored properly.

Get some fresh fuel/oil mix and you probably will be happy.

Share this post


Link to post
Share on other sites

check compression 20+hrs probably time for a new top end,

your reeds should be ok, if you are fouling plugs that bad drop 1 size main jet and then see how it runs, if still fouling plugs drop 1 pilot or main go back and forth till you find what works,

you need to check the power valve on these for deposits also 20hrs you should still be allright but at to rich of a mixture your power valve could be sticking,

if you flick the throttle really fast does it bog, then if you roll the throttle slower it will rev up? if so for sure check the power valve.

old gas can be a factor, did you use stabil? before storing it, even if i think we are riding next week ill still use a little stabil in our gas, fyi 91 oct can already be old at the pump since gas prices are high, i would rather run fresh 85 then old 91 any day of the week.

a little octane booster mixed in with old gas will usually work also so you dont waste your fuel.

Share this post


Link to post
Share on other sites

I have a RM85l also, and when I was breaking in the bike I had the same problem for quite a while. I would not recommend messing around with the carburetor or jetting or anything like that, it will probably make it worse.

When I had the problem I had trouble getting it started, it smoked a ton, was sluggish and would die sometimes if I didn't give it enough gas or even if I gave it too much gas. I fixed all of this by simply reducing the amount of oil in the gas. I forget what I mixed it at, but a good bit less oil then they recommend.

Also, riding it in the higer rpm ranges and getting it going fast helped to clear out what I assume to be excessive oil in the engine.

Edit: Oh, and I went through a crapload of sparkplugs as well. I'm assuming yours are covered with oil? I dont have that problem anymore.

Share this post


Link to post
Share on other sites

I run my kids rm85 at 55 or 60:1 depends on how close I get it to the line on my mesure cup.

How ever I am using MotorX 2s oil. It can be ran upto 100:1. I strongly believe crappy oil will foul plugs like no other especily running it that high of a mixing ratio.

I do not suggest running your bike at higher then 40:1 with crappy oil though. Not worth the risk.

Either buy MotorX oil or Amsoil dominator Thats the only two oils I will ever put through two strokes.

I go through 1 plug every other month this last plug was in for a long time till we had a head oring failure due to me not cheacking the torque on the head bolts.

Share this post


Link to post
Share on other sites
I have a RM85l also, and when I was breaking in the bike I had the same problem for quite a while. I would not recommend messing around with the carburetor or jetting or anything like that, it will probably make it worse.

When I had the problem I had trouble getting it started, it smoked a ton, was sluggish and would die sometimes if I didn't give it enough gas or even if I gave it too much gas. I fixed all of this by simply reducing the amount of oil in the gas. I forget what I mixed it at, but a good bit less oil then they recommend.

i cant even begin on where that is all wrong,

there is no such thing as to much oil even 18-1 can be run in bikes without fouling plugs, if you switch to anything over 32-1 then you are just asking for trouble in a small motor that turns 14,000+rpms.

not learning how to jet a carb is just lazy.

you could have easily jetted your carb to run with a 32-1 mixture which is what the oem recommends on most bikes.

we run ours at 28-1 with zero problems compared to others that have ran bikes with less hrs not as hard that eat thru lower bearings running 50-1 in these bikes doesnt matter if it klotz synthetic or a cheap non synthetic like spectro. if you want some real good answers on this just look up a member by the name of chokey and read any of his posts on jetting or oil, he can better tell you why you are wrong then i can.

and why to run 32-1 or 20-1 or even 28-1 in these bikes and why you jet for it.

more oil is good:thumbsup: less oil is bad, :thumbsup:

would i want to run my truck that holds 5 qts with only 2.5 in it? its the same thing in a 2t motor.

Share this post


Link to post
Share on other sites

Agree that not learning to jet properly is just plain LAZINESS, period !:thumbsup:

In this case however, I think the poster's problem lies within using bad/old/stale gas.

I won't run less than 32-1 in my RM 250 and primarily ride trails with not a lot of WOT. I won't run less than what I consider the best in oil either, Klotz R50 or Klotz Super Techniplate.

Maybe supposedly too much oil, but I like top ends that last, and I absolutely HATE having to replace case bearings. I do what it takes to take care of them. I change my trans oil after EVERY weekend of riding with Klotz FlexDrive 30 as well as I like LONG gear and clutch life.

Like the saying goes, you can spend a little more now, or a LOT later.

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×