Rehab thread roketa

[Ariel Red Hunter]

Originally Posted by Angus67

I may. I’ll check with a unlit propane torch tonight

I don't think that propane is as good as oil at detecting vacuum leaks. If the idle steadies or goes rich when you squirt oil, it proves a vacuum leak. And if you see a puff of blue smoke out of the exhaust during this test, it reinforces the evidence of the idle changing...ARH

[Angus67]

Taken into consideration. What kind of oil? Sowing? Motor oil. Seems alot messyer than propane

[Ariel Red Hunter]

Originally Posted by Angus67

Taken into consideration. What kind of oil? Sowing? Motor oil. Seems alot messyer than propane

Any oil that's thin enough to pump out in a stream and is petroleum based. It doesn't have to be real messy, just squirt some oil on the connection between manifold and engine, carb and manifold. These are the prime suspects. If that doesn't find it, then i'd spray the entire manifold, possibly defective...ARH

[franque]

Another alternative: spray carb cleaner! If the idle speed goes up, you have a leak. It's also good for verifying spark if you have bad gas, or if the carb needs cleaning. The general rule, if it runs on carb cleaner, the carb needs to be cleaned. For testing for leaks though, just spray on the outside.

[Angus67]

Well, shoot. I thought ide check the tightness of the carb to manifold bolts. Apparently the washers i used were not thick enuf, allowing the nut to bottom out on the unthreaded part of the stud. So they stripped out. Need to grab another

[Ariel Red Hunter]

Originally Posted by Angus67

Well, shoot. I thought ide check the tightness of the carb to manifold bolts. Apparently the washers i used were not thick enuf, allowing the nut to bottom out on the unthreaded part of the stud. So they stripped out. Need to grab another

Can't you just use nuts and bolts with washers, instead of replacing the manifold?....ARH

[Megadan]

Yep, you can. Likely an m6 x1.0 thread. I removed the studs from my tt250 manifold for other reasons. The only downside to using bolts is that you only get maybe 4 or 5 threads of engagement into aluminum, so the studs are definitely the better route to go in terms of strength

[Angus67]

Good thing the mani’s are cheap. One is now on the way

[Ariel Red Hunter]

Originally Posted by Megadan

Yep, you can. Likely an m6 x1.0 thread. I removed the studs from my tt250 manifold for other reasons. The only downside to using bolts is that you only get maybe 4 or 5 threads of engagement into aluminum, so the studs are definitely the better route to go in terms of strength

I would not recommend that approach, then. The rule of thumb for steel or bronze bolts was thread engagement at least equal to the bolt diameter. For threading into aluminum, thread engagement of one and a half times bolt diameter, or more. There were exceptions, but those were for not totally torqued nuts, like steering head bearings, and cup-and-cone wheel bearings...ARH

[Ariel Red Hunter]

Originally Posted by Angus67

Good thing the mani’s are cheap. One is now on the way

It is easy to warp the flanges and cause vacuum leaks by over tightening the bolts. When you put it back together, grease on the flange helps the o-ring to seal...ARH

[Megadan]

Originally Posted by Ariel Red Hunter

I would not recommend that approach, then. The rule of thumb for steel or bronze bolts was thread engagement at least equal to the bolt diameter. For threading into aluminum, thread engagement of one and a half times bolt diameter, or more. There were exceptions, but those were for not totally torqued nuts, like steering head bearings, and cup-and-cone wheel bearings...ARH

You could get close to a 1.5 to 1 thread vs. diameter if you get the bolt length exactly right, but I would still rather use a stud given the quality of the aluminum the threads are cut into.

[JerryHawk250]

Originally Posted by Megadan

I would still rather use a stud given the quality of the aluminum the threads are cut into.

I agree and would Loctite the stud. You would eventually wear the threads out or possibly strip in the aluminum with a bolt in the aluminum just from removing and reinstalling.

[Ariel Red Hunter]

Originally Posted by JerryHawk250

I agree and would Loctite the stud. You would eventually wear the threads out or possibly strip in the aluminum with a bolt in the aluminum just from removing and reinstalling.

Yes, so would I, but I get the feeling that we are talking about two different scenarios here. I think you guys are talking about the new 'manifold', and I originally was talking about saving the one he had already stripped the threads in. That was the idea of using a thru-bolt, with washers and nut on the other end. I thought he could through drill it, and then, even if he had to Dremel a deeper flat on the bolt head, and the washer, it would be better than studs in poor quality aluminum castings....ARH

[Angus67]

BBthe one i replaced bolted up fine, but the rubber was badly cracked. And I did locktite the stud in. No matter. When the new new one gets here i will use a much thicker washer. The studs on these are long enuf.

[Ariel Red Hunter]

Originally Posted by Angus67

BBthe one i replaced bolted up fine, but the rubber was badly cracked. And I did locktite the stud in. No matter. When the new new one gets here i will use a much thicker washer. The studs on these are long enuf.

I must have gotten it wrong. I thought you screwed up one of the new ones you got by over tightening the nuts and pulling the studs out of the new manifold. Sorry I got it wrong...ARH