Replacing gaskets
 

Hi, , I need to replace the leaking gaskets (cylinder head and cylinder) but I am not sure if draining oil before taking off the cylinder head is needed. Screws at the cylinder head are loose and learned that oil is leaking slowly since I cleaned an oil spot under the bike. I know Spud drained the oil when rebuilding the engine but not sure if needed when doing the cylinder gaskets.

:thanks:

If it were me, I would drain the oil. Oil is cheap and you probably need an oil change any way!

It isn't necessary to drain the engine oil when removing the cylinder and cylinder head, either to rebuild the top end of the engine, or to replace gaskets. However, I suggest you try tightening the bolts first; you might stop the leaks without the need to replace the gaskets. ;)

Use a torque wrench when tightening the bolts. You can find the torque specifications in the the Yamaha TW200 Service Manual, which you can download at the following link.

http://api.viglink.com/api/click?for...0Manual%20(PDF)

I agree with Spud; just try tightening the fasteners first. Please let us know the result.

I was gonna do the top engine rebuild but after watching spud´s thread I felt a little bit overwhelmed. I will pay someone to do it for me (any shop willing to take my money)I will drop by or call available shops to find out which is better and cheaper. Replacing gaskets will cost me around $73. After two months of oil change and 300 miles, I check the level and added about 100 ml for the proper level. I think the engine leaked too much oil after 2 months and want to fix it ASAP.

You can probably save a lot of money by purchasing a complete gasket set from Taobao. ;)

http://item.taobao.com/item.htm?spm=...cket=19#detail

Hi guys, long time I haven´t post it here. I have time to do the top end rebuild but I can´t remove the bolts. I follwed Spud´s advice but the bolt won´t go any futher (see the pic). I don´t want to remove the engine, please help.

http://i123.photobucket.com/albums/o...1.jpg~original

If you reduce the photograph in size by 50%, it will be much easier for us to view it. ;)

I suggest you remove the nuts from the ends of all four bolts. Then remove the difficult bolt last. You can tilt the cylinder, if necessary. ;)

I will try, Thanks Spud.

I had to remove the engine because I learned that bolts have a flange (not sure if about the right name) on the low position. This made it impossible to remove it (sorry for the crappy pic).
http://i123.photobucket.com/albums/o...2.jpg~original

Then, I remove the engine and found valves are dirty
http://i123.photobucket.com/albums/o...a.jpg~original

piston same as valves
http://i123.photobucket.com/albums/o...8.jpg~original

http://i123.photobucket.com/albums/o...6.jpg~original

Also I found a hole in the cylinder head (upper right side). Probably, this is affecting the performance of the engine and don´t know if the hole must be fixed.

http://i123.photobucket.com/albums/o...0.jpg~original

Finally, I went to the shop asking about rebor and the machinist said yes but will do it until next Monday due to holidays.

http://i123.photobucket.com/albums/o...e.jpg~original

Feedback is welcome.

I don't see a hole in the cylinder head. Are you talking about the chip/indentation located at 1 o'clock in the photograph below?

http://i123.photobucket.com/albums/o...0.jpg~original

If you actually have a hole, you can patch it with JB Weld, et cetera. Otherwise, you don't have any problems. ;)

Have the machinist bore and hone the cylinder to match the smallest oversize piston you can find. You can order a piston for the Yamaha TW200. Besides the oversize piston, I suggest you order new piston rings, gaskets, and valve stem seals. I also suggest you have the machinist clean the cylinder head, and lap the valves for you.

Yep, at 1 o´clock. I will patch it. What kind of valve stem seals do I need? Only the tw200 piston will fit or any other piston fitting the pin? (obviously same size of rebore).

:thanks:

All the parts are TW200 parts. Every recent model year of the TW200 should be fine, but you can select 2006, Yamaha TW200 parts, if you like. ;) I would also order a new piston/wrist pin.

Is the cylinder scored? Is there a ridge at the top that you can catch with a fingernail? If no, then you might not need to bore the cylinder. Just buy a cylinder hone (meant for an automotive master cylinder) and hone it as is. Install new rings and gaskets and enjoy the bike.

It's rare to need to bore a motorcycle cylinder, until there are several thousand miles on it.

That might just be an oil drain-back hole.

That's true; I forgot to ask how many miles are recorded on the odometer. ;) Has the engine lost power, or is the engine burning oil? If neither case is true, I would hone the cylinder, clean the piston, and install new piston rings and new gaskets. :) However, I would still clean the inside of the cylinder head, lap the valves, and purchase new valve stem seals. ;)

No, that photograph of the cylinder head is inverted. The area just below that imperfection is where the cam chain descends to the crankcase. ;) I don't think that imperfection is an actual hole, or anything to worry about. It appears to be a minor imperfection in the casting. :shrug:

It has 27,500 miles, lost power a bit (will not go beyond 90 km, used to go up 100 km). Burning oil? I would say no.

Weld, the cylinder is not scored but there is a ridge in one side at the top.

Based upon your answers, I think you are wise to bore and hone the cylinder as you planned. :)

Agreed. That's a considerable number of miles.

Spud, what piston size I should order from Yamaha TW200 (0.5, 1 mm, or standard) I measured the cylinder (X 66.54 and Y 66.59 mm at 15 mm from the cylinder top not as the manual says 40 mm) and piston skirt diameter (67.09 mm). The piston-cylinder clearance is obviously greater than 0.1 mm limit and not sure the piston size I need. There is number at the piston skirt (inside) I can´t read. The guy at the shop ask me for the this number to get the next size before rebore (my fault I did not take the piston to the shop but I will this fri).

Thanks

One should always take the new piston to the machinist before he bores and hones the cylinder. If a competent machinist has the new piston, he should be able to do the job correctly. ;)

Hector, it is a good idea to choose the smallest diameter you can, so you have more bore options in the future. Take your cylinder and piston to the machine shop to get their opinion.

I went to Yamaha dealer and bought the 0.05mm piston, rings, and clip, parts will arrive in 40 days (last time I bought the gaskets, they arrived in 20 days). Meanwhile, I dropped the cylinder head at the shop for cleaning and seat valves. I am getting rid of dirt (oil and dust in the rear arm) and will send all plastics and gas tank for painting in red (gas tank) and white (all plastics) although the frame is black (the saddle is red color). Any suggestion? Also, I will reduce in length the exhaust 20 cm because the turn signal always get dirty. I am taking advantage of winter and am not in a rush of doing everything in one shot.

Saludos chineros (chineros are called people who ride a chinese bike).

You are making good progress. I suggest you also order a new piston pin, which connects the piston to the connecting rod on the crankshaft. ;) The piston pin is part #10 in the following diagram.

http://images.powersportsnetwork.com...HAFTPISTON.gif

The piston pin is Yamama part #58L-11633-00-00.

Got it already, I forgot to mention.

Hector, where is it winter in Mexico? I'm sitting in PV right now, and it is beautiful outside. I think it is about 28C.

Chineros! I love it!

If you´re in Puerto Vallarta (PV, not sure what PV stands for) what a lucky chinero you´re. Here in Chihuahua (north of Mx) temps are between 0-5C by morning and around 10-15C at noon. I love riding when temps are above 20C. I spent my winter vacations in PV, 2013 and hopefully will spend a couple of days in Cancun next late-March.

Saludos

I was actually north of Puerto Vallarta, in Bucerias. I'm home now, and it is 8C here right now; not too bad.

Chineros, I am in the process of engine assembling. I need to tight the cylinder hed bolts but I am confused. Zongshen uses cylinder head bolt 8-12 N.m, connecting bolt of cylinder head 10-12 N.m, and cylinder head nut 20-30 N.m. Yamaha TW200 recommends cylinder head bolts 22 N.m, socket head bolts 20 N.m, and bolts 10 N.m. Should I use only tw200 recommendation or zongshen?. By the way, I don´t know what exactly are connecting bolt of cylinder head and cylinder head nut (there is no figure).

Saludos

If you post photos of the bolts/nuts, we can help you to determine the torque values. ;)

Since the two engines are virtually identical, I always use the Yamaha torque specifications. ;)

I google the cylinder bolt and nut and they are the same as tw200. Thus, I will use yamaha specifications.

Gracias y Saludos

:tup:

Hi, I assembled the engine but notice the cam chain tensioner is diferent from Spud´s one and that mentioned in tw200 service manual. I wonder if mine is incomplete since it does not have the bolt that spud´s tensioner has.

http://i123.photobucket.com/albums/o...r.jpg~original

http://i123.photobucket.com/albums/o...z.jpg~original

Also, I learned that the chain is very tight when installing the tensioner. I am confused since tw200 service manual recommends a 0.5 mm of tensioner rod position. Mine is about 0.11 mm and can´t adjust it ´til 0.5 mm. The next video shows the difference in tension when releasing the spring (tension cam chain) and when the spring is compressed (loose cam chain)

In other words, the tensioner can´t be adjusted.


http://i123.photobucket.com/albums/o...psyng5pzlh.mp4

The tensioner is automatic. When you release the screwdriver the tension is set properly. Your tensioner is working as it should.

You are missing the end bolt which keeps oil in the engine, and dirt from entering the engine. :ohno: Can you find another bolt which fits the hole?

I did find a bolt for the tensioner. The gas tank is at the shop for painting (red mustang). I checked the plug and is white. The drill bit I used for increasing the size of the hole in the main jet is 1/16" (1.58 mm). When riding at low speeds or 2/4 of throttle the plug is black but at 3/4 o 4/4 of throttle the plug is white. Because I´m out of money these days (I went to the beach), I want to increase the hole´size but I am afraid the drill bit size will be 5/64" (don´t think will find an intermediate size 1/16-5/64"). Also I will cut over 27 cm of exhaust and not sure how this will affect the carb. I mean, will need to increase jet size or decrease?

Saludos Chineros :yay:

Personally, I would not drill the carburetor jets. ;) Mikuni main jets are very inexpensive, if purchased from the following vendor. :)

https://www.rockymountainatvmc.com/p...uni%20n102/221

https://www.rockymountainatvmc.com/i...n102-221-2.jpg

You can learn more about carburetor jets for you Zong by reading the following threads. :)

http://www.chinariders.net/showthread.php?t=6501
http://www.chinariders.net/showthread.php?t=6528

Jets are even cheaper when purchased directly from China. Shipping is often free.

I drill jets occasionally, but I use a numbered drill bit set that has many sizes in between the typical 64ths.

1/16th is way too big for a main jet. I have drilled jets and you use a oriface drill set and a pin vice to hold the bit. I can't give exact sizes off top of my head, they are out in the garage/shop. You can solder a too big jet completely shut and start over. There are charts on the internet that give the hole size that corilates with jet sizes. John