Other '87 Honda XL250R running hot/pops oil/jetting?

[Tubecatgs]

Ok, just spent a summer bringing back to life (minor restoration) of a Honda 1987 XL250r from the grave.... If I knew then what I know now I would have just bought a newer running bike. I like these projects but over budget and this model is really a 2 year model bike and parts are really hard to find... This includes overpaying for a NOS dual carb set up from overseas.... haha

Anyway, finally got it back from the shop as they did a top end rebuild for me and installed the new carb and got it running. Starts good and idle good. However, after I ride it and it gets warmed up, it starts to pop a bit at an idle only. I am running Premium 93 octane (all I can get around here). I haven't looked at the plug yet but I was told thee bikes like to run hot and should go with one size larger jets (should that be a main jet one size larger)?

Also, what oil should I be using. I have heard synthetic oil has a lower break in viscosity of some sort (probably saying it wrong), providing less friction meaning the bike might run cooler. I live in Buffalo NY and will be mainly trail riding on my own 76 acres... no racing, not super aggressively etc. I had Yamalube 20w-50 I think but should I run a 10w-40 synthetic like an Amsoil motorcycle 10w-40 motorcycle oil or I have heard Castrol Power 1 Synthetic 4T Motorcycle Oil is really good.

Any ideas on how to keep this bike running cooler? I can email a video of the sound it makes when hot and idling if you PM me your email address. Here are some before and after pics....

 

[2Wheels]

Been there almost did that. Saw the light at the end of the tunnel and realized it’s the hole in my bank account left by a locked up ‘84 xr, so I abandoned the idea. Ah well, yours is going now that’s the important thing. it’s a well built bike but the xr motors don’t like to be overworked. A kid might wring it’s nexk but you’ve got too much invested to try and destroy it.
Can’t nelp on the oil, pick your poison. Are you using the choke to warm it up?

Oh wait I just realized your that dude in the other thread

 

[Mihylo33]

Sounds like it’s running lean.
Run most any oil you want in it.
Rotella 15w40 seems to be ticket on a lot of 4Ts. Cheap and available EVERYWHERE.

Post a picture of the plug. The electrode end of the plug that is.

 

[2strokesteve89]

Nice job on the aesthetics, so on the idle issue, does it run better on the choke? If it does it suggests what Mike said about it running lean is true. Try adjusting the air/fuel adjustment screw, basically with a warmed up engine run the screw in all the way (but don't crank the screw down, just lightly seat it) run it out about 1 1/2 turns, then start the motor and run the screw in until the engine stumbles, then start running the screw out untill it runs smooth and the idle doesn't improve anymore. If the carb doesn't adjust this way it suggests you have an air leak probably on the boot going to the engine, it may also mean you have dirty carburator passages that need cleaning.

 

[Tubecatgs]

Thanks guys. I will check the service manual I just got and use your suggestions on the air screw mixture. Yes I used the choke to warm it up.. idles high with the choke on but I think that is to be expected. Here are some pics of the spark plug. It only has about 3 or 4 runs of about 10-20 minutes on the plug. it does look like it is slightly tan? Will keep you posted and thanks again for your help.

 

[Tubecatgs]

Ok, After looking in the service manual it doesn't look like they want you to adjust the air screw as this is factory set and has a cover that you have to break off to get to it. Please note this is a dual carb set up. In fact these were brand new NOS carbs I found wrapped in plastic in original boxes that were still factory lubed a bit. I will do it but maybe thinking I try changing the jets first since I am not sure I can get another air screw limiter cap.

A guy I bought the air box from said that these bikes run hot and if it does try 2 things... 1) make sure the gas tank lid vent works and to put the next size up jets in it. So based on the fact that it runs good when cold, only pops when warmed up and by the plug it appears to be running lean.... Which jets should I upgrade? The book shows a needle jet, slow jet and main jet...plus the actual jet needle. any ideas? thanks again all.

 

[2Wheels]

So it runs good until you turn the choke off? How does it behave at different throttle openings? Is the lean pop just at idle or elsewhere?

 

[Tubecatgs]

It starts good with the choke on AND I give it gas on the throttle. After 15-30 seconds or so I turn the choke off and it idles down (but I think that's fine), it runs good for 10 minutes or so while I ride it until it gets really warmed up. Then when I stop and idle it pops. If I stop and idle and it pops and then I take off again it's fine until I stop and idle again... then it pops again at idle. It looks like there is no air screw cap as I just mentioned and in the diagram that needs to be broken and it is currently set at 1.5 turns out so I am gonna start it, warm it up and then try messing with the screw first.

 

[Mihylo33]

It starts good with the choke on AND I give it gas on the throttle. After 15-30 seconds or so I turn the choke off and it idles down (but I think that's fine), it runs good for 10 minutes or so while I ride it until it gets really warmed up. Then when I stop and idle it pops. If I stop and idle and it pops and then I take off again it's fine until I stop and idle again... then it pops again at idle. It looks like there is no air screw cap as I just mentioned and in the diagram that needs to be broken and it is currently set at 1.5 turns out so I am gonna start it, warm it up and then try messing with the screw first.

I would buy one smaller and one larger pilot and main jet for each carb. What’s your elevation and air temp?

 

[Tubecatgs]

Thanks. I live north of Buffalo NY where the elevation is about 50 ft above sea level and will never ride anywhere above 2000 feet. Summers get to about 90 degrees tops only for a few short weeks. Mostly will be riding in 50-75 degree weather. Oh and turns out there is no limiter cap on the new carb so I was able to play with that.. I turned it all the way in, and it was set at the factory at 1.5 turns out. I was able to back it out to about 2.5 turns and seems the popping slowed way down, then I turned up the idle (seems a little high). then the popping almost 100% went away. However, it was 55 degrees out at night and didn't ride it hard on the trails to get real hot (will probably react differently in the summer when its 80-90 degrees out...) but seems better. Will ride it more over the next few days.... Still thinking I might need to go up one jet size but we'll see... Thank you!

 

[Mihylo33]

Thanks. I live north of Buffalo NY where the elevation is about 50 ft above sea level and will never ride anywhere above 2000 feet. Summers get to about 90 degrees tops only for a few short weeks. Mostly will be riding in 50-75 degree weather. Oh and turns out there is no limiter cap on the new carb so I was able to play with that.. I turned it all the way in, and it was set at the factory at 1.5 turns out. I was able to back it out to about 2.5 turns and seems the popping slowed way down, then I turned up the idle (seems a little high). then the popping almost 100% went away. However, it was 55 degrees out at night and didn't ride it hard on the trails to get real hot (will probably react differently in the summer when its 80-90 degrees out...) but seems better. Will ride it more over the next few days.... Still thinking I might need to go up one jet size but we'll see... Thank you!

Yeah you needed to go up 1 on the pilot