Elsie questions

[silverstrom]

Tinkered around some more with my bike. Took the airbox lid and filter off and now it pulls good! Put the lid back on without the foam and it's dead again. Pulled the rubber out of the lid and tried again and it's no better. Either there's something happening when I put the lid on that's restricting it or there is something happening in the carbs. I have a plastic piece leftover but it looks like it goes under the seat. At least I know it's not a motor or ignition problem! Bike felt pretty strong when it revved. Gonna be a super fun bike to ride for sure!

Just as I thought back in early October. Leave the lid off and go do a plug chop. That will tell you what you need to know. Don't worry so much about the jet number, but rather give it what it needs.

You want to think it's running rich if you pull the airbox lid and it runs much better, but sometimes it isn't so much a matter of rich or lean as we tend to think of it, it's a matter of ratios and efficient combustion. There are many bikes that simply need more air to work efficiently. Provide more air and jet up a bit if necessary and you transform the machine. In my experience all 86-90 RZ350s are like that. Early RZs and LCs can benefit from the same thinking.

[Blacklc]

I get that but how did the bike ever get ridden before? No way it ran like this! It still doesn't feel right in the 1/4-3/4 range. But once it hits 6000 rpm it pulls good. Was wondering if the fuel tank could be somehow restricting the airbox? Just want to make sure I'm not jetting around a problem instead of repairing it that's all.

[seahorse]

Interesting outcome and good news that a direction has been found. . now how to solve it completely.
EG feeding it filtered air and enough fuel.

There are a lot of mybee trys I will mention based on what you mentioned " running better with the lid of".
Pipes are they carboned up at the header, ( maybe worth de carbon and de oiling)
Pods ( worth a try ? )
Airbox lid drill, a new dry filter, a 200 main and clip pos 1 ?
As silver mentioned give it what it needs and do a plug chop.
That need just maybe a smaller main with your filter in, id still try a 180 and see if it comes on the pipe, if it does then chop it and have a look and see if its to lean. If it is then ive got nothing.
But good news all the same that some progress has been made.

[silverstrom]

I get that but how did the bike ever get ridden before?

I've said that about many bikes I've bought. Maybe that's why they were sold.

[Blacklc]

I know the original owner of this bike! It ran fine before. Mind you that was 30 yrs ago. I will try the 180s and see what happens. I also have new needle jets coming also. I have one already. Should have the other next week. I can't stress enough that with the lid on the bike is basically not usable. It's not just a bit rich, it will barely do 60 km/h. I'm just glad I'm getting something figured out.

[seahorse]

Its really good news that you are getting somewhere, and there are lots of great guys here that will help where they can like silver and a whole bunch of others.
Without getting completely off track do you know if your domes on the head are original, or have they been machined and have you measured your squish. silver mentions ratios and combustion.
Last year I had and rz head machined with a slightly wider band sharper edge to a bigger volume in the dome, and that took a leaner than I expected main with Kenny pipes. Interestingly it had a slightly lower compression than standard on a new build. I was astounded on the outcome of that jetting issue thinking it would need more fuel, at least with pipes I usually go up 2 mains when I start off. But it ended up taking a 220, anything bigger and like your issue would fall flat on its face.
So if your head has been machined or your squish is unusually large or your compression is slightly low, combined with pipes that don't breath that well on a good day, may result in the situation you have. And making progress towards fixing.

Food for thought, and keep at it.

[Blacklc]

Heads are untouched. Only thing I noticed is that the boots between the carb and airbox are actually smaller than the carb throats! Is this normal or could they have shrunk while sitting all these years? Looks like a huge restriction to me! Are these FPP pipes no good? It sure sounds nice

[Blacklc]

Also I used winderosa gaskets I believe. I know in the snowmobile world some head gaskets are too thick and this causes the same type of problem! Just thought of that now....

[2cycle]

Tinkered around some more with my bike. Took the airbox lid and filter off and now it pulls good! Put the lid back on without the foam and it's dead again. Pulled the rubber out of the lid and tried again and it's no better. Either there's something happening when I put the lid on that's restricting it or there is something happening in the carbs. I have a plastic piece leftover but it looks like it goes under the seat. At least I know it's not a motor or ignition problem! Bike felt pretty strong when it revved. Gonna be a super fun bike to ride for sure!

It almost sounds like there maybe some restriction in the air box.......maybe some debri or a critters nest. Be certain that the air box is clean. I had a very similar problem with my lc not reving up under load but it turned out to be dirty carbs . Stick with it and you'll figure it out.

[Blacklc]

I had the airbox off the bike. Cleaned it in solvent tank then degreased and pressure washed it.

[seahorse]

What plugs are you running br8 or br9
Have you measured squish
Have you done a compression test
Those pipes are fine.
On a side note I just finished another Lc literally yesterday. It temporarily has 51l pipes and I'm running pod filters so I put in a 230 main, 22.5, pilot 5ki needle pos2 ( second grove down) bike pulls very nice from the bottom. I'm at sea level and it will be 37 degrees today or just over a 100 old school.

[JonW]

Put up a piece of the bit of plastic you had left over...

SH, if youre running LC 250 cyls with the 51L pipes, you should have good runner there, in fact I wonder if the 350 LC would work with them quite well too as those are said to be decent flowing pipes. Actually reading your jetting, im thinking its 350 from what youve said... and if so you might want to go bigger perhaps as youve no airbox?

[Blacklc]

Never measured squish. Compression is 120 psi both sides. Those gaskets are thick! I did a rough measurement on head gskt and it's .040" . Should be .027". That's quite a difference! On a snowmobile that makes a huge difference and makes tuning a nightmare! I'm gonna order up a yamaha gskt and compare. Makes sense to me....

[seahorse]

I have a Haynes 80 - 82 Lc manual I front of me as we speak.
Believe this or not early 250 is a 190 main 350 is a 160 main with the 4 n10 and 4 h16 needle combinations. Then on page 96 they went to a 220 main with the 5k1 needle ,22.5 pilot.

JW the 51L pipes and pods with the 230 mains are fine at the moment. 37 degrees (100) yesterday at sea level and it's blowing smoke and the plugs are very dark so it's still running rich. But clean and strong. I'll be getting cigars for her and the 51L pipes will be going on another RZ I'm about to begin building.

[JonW]

Ok, just didnt want you to go bang. 350 cigars? if not you will be losing performance I'll wager over the 51Ls...