I just picked up a Graydon Proline pipe for my son's LT50. Does anybody have any experience with this pipe on this machine? I am also looking to put an uni or K&N filter on. Will I need to re-jet? TIA

 

Anytime you increase air flow into the carb you will need to rejet. I also have a stock LTA 50. Do you think the pipe will increase hp much. I went to take out the restrictor and it wasn't there. I was hoping it was. LT 50's may be bulletproof but they are dogs. Have you made any other mods?

 

No other mods other than the intake and exhaust restrictors taken out.

 

You will probably need to re-jet. Should you find a source for pilot jets, post it here please.

I presume you two took out the intake manifold restrictor?

My current mods-
Drilled some 1/4" holes in the air filter cap.
Removed intake restrictor.
Removed first pilot jet; there's 2 in there from the factory.
Needle clip in center position.
75 main jet, stock is 55.
1 step cooler plug.

I thought that I was having detonation issues when the bike got hot. It would stop revving up, but would still idle ok due to what I thought was aluminum ***** on the spark plug electrode. Turns out it was carbon, so I switched to a quality synthetic oil, and hopefully the coming mods will allow the engine to breathe better, but I suspect there will be a need to de-carbon the little bugger occasionally.

One of the best mods I did was grind down the wheel stops until they were flush with the rest of the spindle. That really helped the turning radius, and made it much easier to spin doughnuts.

Today the cylinder arrived back from Forward Motion. I had it bored one size over, and the exhaust ported.

Other mods-
Shaved top of slide until it cleared the carb hole.
Ground off any obstructions in the intake and head.
Dismantled oil injection, premix only now.
Pulled spark arrestor, and drilled some holes in the 6" tube.
Drilled three 1/4 holes in each clutch shoe.
Planning on making a real airbox out of fiberglass, we'll see.

I'll re-assemble the bike next week, but am guessing I'll need a larger pilot. I'll post the results.

 

Yes, I have the intake restrictor out. What does one step cooler plug do? Also, what does drilling 3 1/4 inch holes in each clutch shoe do? How do you do this? Keep me posted on how the bike turns out. Thanks

 

I went to remove the restrictor in the exhaust, per the owners manual, and there was nothing there. Where is the intake restrictor at ? My kids 50 will only do about 10 - 12 MPH on a dirt road...

 

The intake restrictor is in the intake manifold where it goes into the head. Take off the intake manifold and heat the end with a torch. The restrictor with a key slot hole should fall out once it is good and hot.

 

The stock BPR-4H plug is too hot unless you have the restrictors in and your critter is just idling around the yard. Otherwise, go to a cooler plug like a NGK BPR-5H. I'm probably going to end up using a BPR-6H (yet another step cooler than stock) but we'll see.

The idea behind drilling the holes in the clutch shoes is to make them lighter, so it engages at a higher RPM. I suspect it won't make a difference, but can't hurt. The holes are drilled in the end furthest from the pivot point, and on the side, not the shoe surface. Don't bother pulling your clutch apart unless you want to see how it works or I come back with a good report on the new engagement point. The correct way to raise the rpm point is with stiffer springs, but I have yet to find any. The other issue is that the stock motor won't pull hardly any rams, so a higher engagement point could easily turn into a driveability problem.

The intake restrictor is in the intake manifold, the little aluminum elbow between the cylinder and the carb. After getting all the damn plastic out of the way (what was Suzuki thinking?), you'll see it held on by two bolts. Pull it off, and off the carb. You'll see a hardened steel insert, with a hole resembling a key slot. I torqued a screw into it, heated the manifold with a propane torch until the adhesive melts, and pulled it out with vice-grips.

With a few 1/4" holes in the air filter cap, the restrictors out, and the jetting, my son's LT-A50 does 15-17 on flat ground, and up to 22 on a mild downhill, maybe a bit quicker on a cold day. The real improvement was in the acceleration, although the holes in the air filter cap made the intake noise louder than the exhaust. Make sure you pull out the first pilot jet after pulling the restrictors, and a larger main may be needed.

Btw- if the need to hold the brake on when pull starting it bugs you like it did me, pull the cover off and just bend the little metal tab inside a smidge. Easy to see how it works once it's pulled off.

So tonight after looking the modified cylinder over, I decided to do some very basic clean up work to the intake side of the cylinder, and the intake manifold. After grinding for a bit, I checked the ring gap, and began to re-assemble the lil Zuk.

Well- turns out Suzuki made some changes to the motor on the LT-A50 vs the old 84-87 LT50 which used a JR50 motor. The piston pin is bigger on the new quad, something like .629 Vs .487. Arrrugh. A quick call to Eric Gorr (that guy answered the phone at 9:30 PM!!) fixed that issue; he's getting me the right parts drop shipped to my home.

I'll keep you posted.

 

Definately keep me posted. Thanks for all the info. Wouldn't you want the clutch to actually fully engage at a lower RPM rather than a higher RPM? That way the motor could begin pulling the little quad to speed that much sooner than slipping the clutch.

I will try the different spark plug. What size main jet did you go with? I am ordering a K&N filter RU-0200 and a outerwear.


I put on the pipe this Sunday and pulled the first pilot out and put a 65 main jet. I tried running with the airbox wide open and it ran pretty well but I think it wanted more fuel. I put the airbox back on in its stock configuration and it bogged like crazy. I'll let you know how it runs once I get the airbox and jetting dialed in.

 

Think of it as a torque converter. If a converter engages at 1000rpms, the motor's not making much power. If it engages at 6000rpms, the motor's making a bunch of power, and the vehicle takes off much quicker. Like revving a motor up and dumping the clutch Vs letting it out at lower rpms.

These little motors are so anemic that often the quad is unable to take off on even the slightest hill, more rpms will certainly help.

I have a 75 main, and couldn't tell a difference between no filter cap and one with holes drilled in it. Let me know how the RU-0200 fits.