Newbie engine question

[heavyjeff]

Hi, I bought a used trailmaster XRX for my grandkids to ride and want to replace the top end due to lack of pulling power .
The sticker says its a BBVXP.150 CYC 149.6cc . Is it being a Chinese 150 cc all I need to know to order parts? Thanks in advance.

[plee911]

2 bolt or 4 bolt valve cover? And measure your cylinder studs to get the right size if replacing the cylinder.

[heavyjeff]

4 bolt valve cover but not sure about the stud distance

[xlint89]

Welcome to the site Heavyjeff.

Might I suggest you try adjusting your valve clearances first. There's a chance the valves may only need to be adjusted in order to regain some lost power, it's FREE and pretty easy to do if you're handy and have a set of feeler gauges.

You can go on youtube and it will guide you on how to adjust the clearance. Just look up GY6 150 valve adjust.

Secondly, since the buggy is new to you, it wouldn't hurt to go over the Constant velocity Transmission (CVT for short). This is also an easy thing to do if handy and usually very low in cost. It's also a common cause for drive ability issues.

1. Check your drive belt edges for glazing and/or slipping (replace with proper size if found to be the case)

2. Check your rollers for flat spots inside the variator (front pulley with the fan). You will usually need an impact gun to remove the nut. DO NOT use a screwdriver or pry bar against the fan blades to try and hold it in place as you attempt to remove the nut. You WILL break the fan blades.

Not a bad idea to disassemble the variator, clean up the internals, and lubricate the inside with a dry lube. DO NOT get any lube on the pulley faces as that will make the belt slip.

3. If you can, remove the rear pulley's clutch. You will need an impact gun and a large socket to do that. Be very careful when disassembling the rear set up though. The rear set up is under spring tension and you need to pay attention. (again, youtube the procedure)

Also make sure to use the proper socket to remove the large thin nut, and be sure it's squarely on the nut. It's really easy to strip the nut and cross thread it as well. So pay attention. (I warned you)

If you are able to get the clutch apart. Look at the friction material of the clutch arms (they look like mini drum brake shoes from a car) Often times they are glazed up and can be brought back to service by just roughing them up with course sand paper.

Then look at the clutch "bell" is what it's called, but is really like a mini car brake drum. Often it's glazed (shiny and slippery) or in worst cases actually "blued" from the heat.

Once again, can usually be brought back to service with just a rough sand paper.

4. Make sure all the air passages on the CVT cover are unobstructed and the air inlet and exits are clean. Lack of air causes heat, and heat is what usually damges the CVT components.

5. While you're in there, now would be a good time to drain and replace the gear lube as the previous owner most likely neglected this part of the buggy. You'll most likely need an oil can to fill the fluid, but it's not very hard to do. (again check out youtube)

None of the stuff I just recommended costs anything, except a quart of gear lube, and maybe an oil can and large metric socket to remove the clutch bell. Really not bad at all.

Don't be too concerned with the CVT cover gasket as it's not really preventing any fluids from leaking

I would suggest you try this stuff before you go buying anything for the buggy first. You may have a low compression reading, but find out one of the valves is not closing all the way and giving a false reading. So adjust them first before you do a compression test.

Good luck with the buggy. they are a ton of fun.

[heavyjeff]

Thanks so much for the advice! I will try all of this before I buy anything. I have a lot more time than money now adays.
Also, When I said loss of power I should explain a bit.
It runs and pulls fine on flat but when pulling up a incline it starts loosing speed till it stops. The engine is barely running now with the petal to the floor and it has very low rpm. Put it in neutral and it revs fine but still wont pull.
Thanks again for the info!

[liduno]

If it sat unused before you got it, you might want to consider cleaning the carb and petcock. Get rid of the old fuel too.

[xlint89]

Solid advice right there ^^^^

Could be running out of fuel.

Could be poorly jetted and the temperature change can be affecting it too

Could be valve adjustment

Could be very low compression.


I suggested checking the valve clearance first, because a valve "hanging up" can cause low compression. Doesn't necessarily mean the cylinder, piston, and/or rings are bad

[heavyjeff]

Tonight I checked the gap on the valves and there was none.
Found 1 piston ring and the oil rings seized up and piston and cylinder both with numerous gouges.
5 rollers in the variator stuck/froze up in their cradle and 1 was only half the diameter it should have been.
Hopefully after all this is replaced it will be good as new.
Thanks for all the great advice, you all keep it coming cause I am sure to need more in the future!

[liduno]

Wow! That thing had some issues..lol
Luckily, the parts for these buggies are pretty cheap.BUT, since you mentioned you had more time than money. Maybe consider adjusting the valves, cleaning the fuel system, and freeing up those rings?

I only suggest this because it's all free. For just the test, I would even consider reusing the base and head gasket after spraying them with some ''copper spray a gasket'' If you're careful taking the carb apart to clean, you can likely get away with not needing any parts or gaskets for that too. Who knows, it might actually run pretty good with just those fixes.

If the gouges aren't too bad, and it has good compression after adjusting the valves and freeing up the rings, get the rollers for the clutch and you're good to go. If I remember correctly, the rollers are under 20 bucks.

If it doesn't run good after that, consider it a test run for working on that motor. Hopefully you wont find more things that need attention that would make it not worth fixing. I/E cam, valve seats, valves, valve springs, valve guides, warped head ect ect ect.

[heavyjeff]

The gouges in the piston and cylinder are pretty deep so will probably just replace them since as you said they are pretty cheap.
As for the rollers, one of them has wore a big groove in the pocket it sits in so looking for a complete variator.
But I do have a question about the roller weights. What size weight do I want? I have seen 12, 14 and 18 but I would think there are more out there.
I think I will weigh one of the old ones and replace them with what I had unless someone has a better idea. Thanks again.

[liduno]

Originally Posted by heavyjeff

The gouges in the piston and cylinder are pretty deep so will probably just replace them since as you said they are pretty cheap.
As for the rollers, one of them has wore a big groove in the pocket it sits in so looking for a complete variator.
But I do have a question about the roller weights. What size weight do I want? I have seen 12, 14 and 18 but I would think there are more out there.
I think I will weigh one of the old ones and replace them with what I had unless someone has a better idea. Thanks again.

I've seen them as low as 10 I think? They effect the rate of engagement. You would need to decide if you are looking for the clutch to engage sooner or later. If you're getting a whole new setup, I would assume it would come with them already?

[heavyjeff]

Yes you are correct. I found 2 different ones so far, one has 12.5 and the other 14. I am trying to research what was oem but still digging.

[liduno]

I believe I went with 11's on my Hammer Head. It allowed the engine to rev up a little before engaging the belt. It gave me a better launch and didn't seem to effect top end at all.

[heavyjeff]

I guess I need to try out whatever size I get and see what happens, guess if they are too heavy I can drill them out slighty to make them lighter.

[plee911]

From what I have seen most buggies come with heavier rollers from the factory. 13 or 14 gram.

Lighter rollers give you more low end but reduce top end heavier rollers give you less low end but higher top end.

Sliders from what I have seen are kind of in between, IE a 12 gram slider will behave like an 11 gram roller at lower RPM but act like a 13 gram roller at higher RPM.

Im running 13 gram rollers at the moment but plan to go to 11 gram sliders.
This is because I need my buggy to have more low end torque but don't want to lose all of my top speed. Top speed is currently 36mph but I would be happy with 30 if I can get what I need to climb some hills in my area.

[heavyjeff]

Thanks for the advice. Going to "see what happens" with what came with it, But I am not a small guy and want that low end torque for the hills also.

[liduno]

I didn't lose any top end when I went to a smaller roller, BUT! I did lighten my buggy a lot.

[BuggyMaster]

My first thought actually was that variator. Looks like you are off too a good start on getting it going. Fortunately these things are relatively cheap.

[heavyjeff]

I finally got the piston and cylinder replaced and the varistor with 14gm weights installed in the Trailmaster XRX. What a drastic improvement! I can now pull muddy steep trails without too much loss of speed and that's with it loaded down with myself and wife. Thanks for all the advice, you guys are great! Only I think these carts (I have a Baha Dune also) are going to become an obsession as I am currently debating how to get MORE POWER! Being retired now I may have to find a part time job to feed my new addiction.

[liduno]

The addiction is real..lol

[BuggyMaster]

Ya you are done now....lol...but it’s sure a lot of fun