Service
SERVICE
We welcome your technical questions and comments, and will publish those we think are of interest to our readers. Because of the volume of mail received, we cannot return any personal replies. Please limit your "Service" letters to technical subjects only, and keep them as brief as possible. Send them to: "service," CYCLE WORLD, 1499 Monrovia Ave., Newport Beach, Calif. 92663.
BLOWING OIL
My 1978 SR500, when subjected to sustained high rpm, will blow large quantities of oil out the crankcase breather tube. Flow as large as a pint in five mi. has been observed. A catch can is used instead of the airbox and no valving is used in the tubing. An automotive PCV valve (installed to create negative engine pressure compared to the atmosphere) helped some but (opposite what I expected) every seal on the motor began weeping oil. Removal of the PCV valve returned the motor to its afore mentioned condition.
Unfortunately. this is not an isolated case. At Texas World Speedway where speeds are high. no fewer than four out of five suffered this problem (SR's. XT's. TT's alike). Locally, on shorter tracks, at least 30 percent of thumpers seem to be affected.
Furthermore, `engine condition doesn't seem to be a factor. My engine had three races on it with no problem and with no changes whatsoever started blowing oil at the fourth race. Subsequent engine tear down showed the rings had seated prop erly and allowed no blowby. Other affected engines have been in every condition from new to well used, from stock to wild.
The only solution so far has been to run the engine nearly a quart low on oil (hardly the hot set-up) and this only helps. not stops the problem. Any ideas?
"Stormin' Norman" Meyer Conifer. Cob.
We experienced the same trouble when racing a modified TT500 in Baja. By install ing a stock breather baffle canister from a TT500 the problem can be reduced but not completely eliminated. The stock baffle can ister will complete/i' cure the blow-by prob lem by breaking the suction effect that develops at high engine rpm. Some oil useage under racing conditions will still he~ noticed as the 500 thumper seems to pass oil around the valve guides but shouldn `1 be a problem on a track machine.
PROTECT THOSE THREADS
I really enjoyed Don Norris' "All Thumbs Tool Kit" in the December `78 issue of Ci'cle World. Itoohavea 13-15mm socket. I hope the guide will become a regular feature, as several other important tools of the Backyard Butchery" trade were left out. A special set of tools is a necessity for removing those wonderful cross-head screws the Japanese are so fond of using. As we all know the heads of these li'l darlings are made of silver colored sills putty. Through a great deal of trial and error, and cursing. I have put together a tool kit that will allow even the most pitiful of backyard hacks to remove most of the screws on their bike:
1-Phillips screwdriver
2-Impact driver with Phillips hits in as
sorted sizes
3-4 lb. sledge hammer
4-Can of Liquid Wrench
5-High-speed electric drill and handful of bits
6-Set of screw extractors
7-Pair of Vise-Grips
8-Hacksaw
9-Patience and two six-packs of beer.
Tom Stevens Pembroke Pines. Ft.
A Ithough `our letter was written with tongue-in-cheek, your point is well made. Japanese cross-head screws can he yen' frustrating to remove. Part of the problem is caused hi' differences in cross-head screw driver shapes. Mani' have sharp/i' pointed ends that bottom in the screw head befoi-e the sides of the screwdriver tip engages vroperly. With this type screwdriver the screw head is instantly stripped. Check all of the cross-head screwdrivers in your tool kit and round the end off any with sharply pointed tips. A bench grinder will fix them etisily.
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BREAKERLESS BSA
I have been looking everywhere for a pointless ignition for my 1972 BSA Single. Any suggestions?
Dennis Thompson San Diego, Ca.
Try CCM Imports, Ri. 1, Huntley, Ill. 60142. Phone (815) 923-2155
COVERED IN OIL
My KZ750 started leaking oil around t~e head gasket at 400 miles and the gasket was replaced on warranty. This helped until about the time the warranty ran outthen it started leaking again. My dealer wouldn't replace it again under warranty but did retighten the head bolts, which didn't help. I went through the same BS ith a KZ400 and am tired of being cov ered with oil. Help!
Steven Jane San Francisco, Ca.
Have a reputable shop tear the engine down and check the head and cylinder iiating surfaces for warpage. If warped they will have to be surfaced or replaced.
ENDURO LIGHTING
We have found that the direct connec 1ion of the existing taillight/brakelight connections to the existing lighting coil on a 1977 1T250 or 1T175 produces an unac ceptably low level of illumination in all rights. We have overcome this problem in two ways. On the 175 we found it expedient to wind an auxiliary coil specifically for the bbrakelight lighting load. It is unreasonable to expect the stock coil to handle a 77 percent increase in load just by adding a wire to use the power.
Using your article "Low Buck Fixes for Lights" as a starting point (Shame on you for forgetting your own article and shame again for not following up on your word, `Instead, we plan to do similar articles on other models as demand warrants.' My~ apologies if I missed it), we hopped up the stock coil, added a brakelight switch and bulb (socket was existing on both bikes), and to keep the bulbs from burning ouv~ when the brakelight is not on added a simple voltage regulator (cost about $4) though a parallel load would do.
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Roy Kitko Sisterville, W. Va.
MORE DT POWER
I have a Yamaha DT175E that has bee~ modified with knobbies and an exhaust system. It works well in the dirt but I need more power. any suggestions?
Joseph N. Welsh Montclair, N:J.
DG Performance can give your Yamaha4 all the power you want. See Cycle World; December 1978 for details or write to DG Performance Products, 1170 Van Home, Anaheim, Calif 92806.
GEMINI PARTS
I have a Gemini 80 manufactured by th~ San-Tong company. I can't find parts for it. Can you help? I need a piston and rings.
Mark Sikora Warren, N.J.
The Gemini 80 used an engine' that looked much like a Yamaha 80. Take the~ piston and cylinder to your Yamaha dealer and have him measure it. With any luck he will be able to substitute Yamaha parts.
