Top end inspection - what do you do?

[Tekime]

Rebuilding an older 4-stroke ('90 DR350) and some of the inspection tolerances are crazy -- like 0.0004" for the rockers, 0.0006" for valve stem wear, etc.

The OEM tools are crazy expensive, about $850 for dial calipers, $300 for 25mm microm, obviously not buying them anytime soon.

I have some cheap digi calipers that have pretty good resolution but I don't know about the accuracy at that precision.

When you guys are rebuilding/inspecting what kind of tools do you rely on? Do you just do visual inspection and replace with new valve stems/etc., or send to a shop, or do you have the tools?

I guess I'm wondering specifically if there is a good dial gauge, micrometers, dial calipers that you actually rely on for these tolerances without dropping over $1k.

[Kurlon]

if I have reason to suspect the valves/guides/rockers, typically they're cheap enough for older air-cooled mills that I'll just replace'em. Only bit that sucks is for valves/guides is I have to send that to an expert but still doesn't cost that much.

[Paul_E_D]

Yeah, those aren't typically even inspected in a top end job. It usually refers to replacing piston/ring/wrist pin. Head work is a different story, and usually done at a machine shop. I have sent my head out to mxtime and had new valves/guides, and seasts recut for about 300 buck I think.

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I should say, it's only really necessary if your valves are going out of adjustment quickly...

[Tekime]

Cool. I'm just being nitpicky going through the service manual. Already have it torn apart so checking what I can in the process. No reason to think they're out of spec per say, and I've got plenty of good spare parts. I am a bit fascinated by the process and would love to have some adequate tools to check this stuff someday, more for curiosity than economy I guess. Money I could be saving for Penguin though

[Rada]

Those tool prices are stupid. You can buy real deal top shelf machinist tools for a small part of that price.

Like Paul said, generally the only thing you you typically check in a DIY situation is valve clearance and that is done with a $12 set of feelers. Actually you can do a good job of checking piston to cylinder clearance with the feeler too as well as ring end gap. This will tell you quickly if you are worn out of spec. The only time you need real measuring tools is then you are boring and honing the cylinder to make sure you have it round and straight. Again, unless you have a machine shop you won't be doing this at home.

Have fun learning. It's a ball working on engines and learning about what matters to make them run.

[Tekime]

Those tool prices are stupid. You can buy real deal top shelf machinist tools for a small part of that price.

Okay, that's kind of what I was hoping. I've usually been able to find alternatives for much cheaper than the Suzuki tools but don't have much experience with the high-precision instruments to go on. Was thinking about the cheapo HF dial gauge but now convincing myself to skip a lot of these (probably unnecessary) measurements at least as far as this rebuild is concerned.

Like Paul said, generally the only thing you you typically check in a DIY situation is valve clearance and that is done with a $12 set of feelers. Actually you can do a good job of checking piston to cylinder clearance with the feeler too as well as ring end gap. This will tell you quickly if you are worn out of spec. The only time you need real measuring tools is then you are boring and honing the cylinder to make sure you have it round and straight. Again, unless you have a machine shop you won't be doing this at home.

Done valve clearance on a few bikes but checking cylinder clearance with feelers is new to me, cool. Cylinder/piston are in good shape I think, will throw some new rings in for sure. I don't know about having a full blown machine shop anytime soon but not afraid of investing a bit in some better tools over time.

Have fun learning. It's a ball working on engines and learning about what matters to make them run.

Thanks! I've always maintained my own cars, done quite a bit of work outside the case but only started tinkering on small engines the last few years. Completely fascinating, and something I can actually do in my shed. I've been tearing apart computers since I was a kid, but combustion is an entirely different ball game!