DT175 1978 Posted October 19, 2012 Share Posted October 19, 2012 Hi guys. Me again. I have posted about this bike and these issues, but I’m starting a new thread with my new updates for the sake of clarity. I’ve checked out a few more things, but have yet to find the major issue. I apologize in advance that this post, and most posts I ever have or ever will make, may be a little long. That’s how I am. The bike is a ’78 DT175. It sat for an unknown period of time, probably very long, and I’d I’m trying to restore it to service with the least amount of hassle. I do not know why it was parked. Here’s what I’ve done so far: Drained out the old gas and inspected the tank – it is rust free and clean. Filled tank with quality name brand 89 octane. Removed fuel petcock and cleaned, including screen – it’s good. Installed a new OEM air filter, heavily oiled with PJ1 foam filter spray oil, Cleaned out air box. Installed a new reproduction carburetor – the old one was spewing fuel out the over flow and had no response to adjustments in the pilot air screw, so I bought and installed a new reproduction carb. Attempted to adjust the above mentioned carburetor. Checked spark visually by placing plug against the engine and turning it over – spark is fat and blue, even with a fouled plug. Installed a new spark plug of the proper gap / type. Here’s the problems I’m having: Hard to start cold. When it’s warm, first kick every time, but cold starts are tough. It is difficult to adjust the idle. (This doesn’t seem to change with any adjustment of the pilot air screw.) It wants to idle too high, seems around or above 2000, and if I try to adjust down the idle to where it should be, it falls too low – too low to idle and stay running. There’s no in between. Sometimes the ‘high idle’ will fall to a ‘low idle’, and sometimes that ‘low idle’ will climb back up to the ‘high idle’. (only a couple of hundred RPM fluctuation) When in neutral, and you slowly twist the throttle, it does not seem to reach proper high RPMs. Seems to struggle a bit to raise RPMs. When you try a test ride, it seems pretty normal as you take off (save for the nearly gone clutch) but as you accelerate it quickly begins to struggle just as you get into the power band… it struggles to raise the RPMs and when this happens it sounds less like a motorcycle and more like an ill frog struggling to make a croaking sound… it does struggle and croak and get through it and past that point and back to sounding like a motorcycle, but by then, the RPM’s at are at (or past) the shift point and approaching the red line. Bottom line, it struggles right through the meat of the power band and sound like a dying frog whenever it struggles. Where should I go next? Crank seals like Air Head said 2 minutes after a joined this forum? Link to comment Share on other sites More sharing options...
DT175 1978 Posted October 19, 2012 Author Share Posted October 19, 2012 I have read several posts that seem to indicate that failing crank seals is much more likely than failing reed valve, but I’ve been reading up - I googled crank seal symptom, and I also googled reed valve symptoms and I read several of the results. For crank seals I kept reading: Hard starting, hot or cold, bad idle, runs great in the upper rpms… Well, I do not have hard starting when hot, and it does not run better in the upper RPM range. I’m not too sure that’s desribing what I’ve got going on. For reed valves I read: Idle - rough idling engine that sounds like it is on the verge of dying. Hesitation - Engines with reed valves that are failing can present symptoms of hesitation during acceleration. The engine may fail to respond to the increased fuel flow and then jump forward as the gas is finally ignited. The hesitation in the engine due to failing reed valves can be very frustrating as the power is simply not available when needed Reduced Power - However, failing reed valves reduces the fuel and air mixture. This results in fuel being dumped into the carburetor with no flame to ignite it. The result is reduced power. If the engine is brought up to the higher revolution per minute, or RPM, levels the power may return, but will disappear again once the RPMs drop. Read more: Reed Valve Symptoms | eHow.com http://www.ehow.com/list_7528907_reed-valve-symptoms.html#ixzz29lSYdgPv The failing reed valve symptoms sound about exactly like what I have going on… Link to comment Share on other sites More sharing options...
DT175 1978 Posted October 19, 2012 Author Share Posted October 19, 2012 Where does that leave me? Still checking this mystery carburetor? Should I rebuild the original before I move on? Have a missed anything? What would you check next? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted October 19, 2012 Moderator Share Posted October 19, 2012 The main culprit crank seal is the left hand one that will pass unwanted air into the crank case and reduce vacuum in the carburettor venturi! It's an easy test by running the engine and using a tin of WD40 with spray straw attached...spray through the slots cut into the flywheel sides and aim the jet of spray toward the crank seal. If this action changes the way the engine sounds or runs (briefly) you have just proven the seal is bad In my experience a bad reed valve with curved petals will give slightly less acceleration and power output...along with better fuel consumption and a hotter running engine but starting isnt hard to do! anyway it's another easy test...First by visually seeing if the petals sit flat and secondly if you clean the thing up you can blow air through it but but not suck air through it, I do this test all the time with mine, If you are running after market fiber reeds It's a good idea to turn the petals over the other way every 3 thousand miles or so...this will help to keep them flat and sealing properly Link to comment Share on other sites More sharing options...
Moderator drewpy Posted October 19, 2012 Moderator Share Posted October 19, 2012 Iyou can blow air through it but but not suck air through it, I do this test all the time with mine, giving your bike a blow job! Link to comment Share on other sites More sharing options...
Moderator Cynic Posted October 19, 2012 Moderator Share Posted October 19, 2012 giving your bike a blow job! He obviously 'really' likes the dt. Surely it would be a quicker bike with a blower sat on it......... Link to comment Share on other sites More sharing options...
DT175 1978 Posted October 19, 2012 Author Share Posted October 19, 2012 Thanks again guys. I guess I would need an engine gasket kit before even taking the left side cover off or taking the reed valve out... I think I'd also need some tools that I don't have. I think I'm in over my head. I really screwed up and did cosmetic and street legal stuff first (brand new NOS seat cover, got the plastics looking good, repalced a broken turn signal and front stop switch) and licensed it with perminate collectors plates... I've got a good looking, fully legal bike that runs like crap. Now I'm way over budget and out of skills to get it running right.... I've wasted a bunch of money I'm never getting back and I think I better quit. If I decide to keep working on it, I'll come back and bug you guys with some more questions when I have them, but for right now... I've lost faith and I kind of just want to just push it over a cliff. I keep throwing good money after bad and I just don't believe that after I go buy a gasket kit, an impact driver, a torque wrench, crank seals, reeds... I just don't think I'll get it running. And then there's the clutch and front forks which I know both need attention that I'm not fit to give, I think the financially smart thing for me to do would be to just quit. I've lost faith. This was just a stupid pipe dream anyway, I don't have the skills to fix things and this isn't going to teach me anything... I should have taken up golf. Thanks Airhead for trying to help. You seem to know your stuff. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted October 19, 2012 Moderator Share Posted October 19, 2012 Dont get despondent, you may even be able to do those checks without even repacing any gaskets if your careful and 'tease' the cover off, watch out for the gasket sticking to both the cover and the engine...just gently pry it off so it all stays stuck to the engine case...the reed gasket is pretty sturdy so you'll no doubt get away with that one for now...just grease up the faces when you re-fit them. Then you can buy the gaskets when you're happy with your bike. Here in UK gaskets are cheap to buy (pattern ones) Link to comment Share on other sites More sharing options...
oldbikerehab Posted October 19, 2012 Share Posted October 19, 2012 Where are you in the US? I'll come catch that thing if you're pushing it off a cliff near me. I was in the same boat as you about this time last year and spent at least a month of gorgeous riding weekends kicking my leg off on my beat up DT175E craigslist find with the same plan as you- to rebuild an old bike without previous experience but a decent knowledge of design and things mechanical. Now, I have a DT that runs like a mf and is a blast to ride, on an off road. Yeah, it's got a nasty oil leak but that's because I made the mistake of ordering some generic oil seals off the bay. Now I know. You should check out my intro, it's got a few of the many lessons I learned in the 7 or so months that it took me to rebuild mine. Such as- Don't waste money on tools like torque wrenches etc. If there is some type of large chain auto parts store near you, they usually have free tool rental with a refundable deposit. Though I bought all that stuff and I'm glad I did. Also, keep it smokin'. I didn't understand and blew a hole in my piston. You can do it. Your gray hairs will increase and you will likely curse that bike and wonder WTF you got yourself into. But seriously msg me if you do decide to get rid of it. I'm pretty broke right now (mostly because of all the money I wasted on first timer f-ups on my bike, new tools, parts, paint, chemicals- it adds up) but I'd be interested if it doesn't turn out to be too far gone and you aren't too far away. Link to comment Share on other sites More sharing options...
shambles1980 Posted October 20, 2012 Share Posted October 20, 2012 gaskets arent expensive. engine seals when bought as a kit arent that expensive either.. i would always recomend a reasonably well made 1/2 inch ratchet set. try to make sure the 1/2 inch sockets go down to atleast 12mm "mine go to 10" and then an impact driver is also usefull. and you cant do anything to an old engine without a can of wd40. so id get the biggest one you find. a resaonable socket set with 1/2 inch ratchet and sockets down to 10mm may be a bit costly. but well worth the investment, if you cant affoard the ones with lifetime warranty like snapon...then you can get prety inexpensive ones that have a 5 or so year warranty. and for the price of them "usualy like £40 in the uk" its pretty good value for money. i dont think any one with a motor cycle can survive without a socket set. "prehaps 2 of them" and some spanners. (you often need a spaner on 1 side and a socket on the other to un do a nut) sometimes you can take the cover off and look near the fly wheel and see oil has leaked.. thats a sign that the crank seal has gone.. but the wd40 trick is new to me and i may be trying that one my self.. oh and with the kits if your getting just the crank seal sets. check them when they arrive. i have had people send me 2 of the same side and they should have been different. Link to comment Share on other sites More sharing options...
DT175 1978 Posted October 20, 2012 Author Share Posted October 20, 2012 Hey thanks again guys. I appologise, I was getting a bit dispondant. Yesterday was 'one of those days' and I was pretty overwhelmed with my project along with other parts of my life. Thanks again for the good advice. I do have plenty of sockets,open end/box wrenches, screw drivers, pliers, cresent wrenches and basic stuff - it's really just an impact driver and torque wrench that I need tro be well equipped with tools. They're probably both good ideas. And you guys are right - gaskets aren't that expensive. I need to remember that I went into this with the idea of learning how to fix things - because I'm not good at it and I want to learn - so its not supposed to be easy and I have a lot to learn. I think I need to just slow myself down and re-group myself a bit, and continue on when 'my heart is into it'. Thanks for the kind encouragement. I do want to make this thing run. I really want to go for a ride! I'll try to come back and post when I have specific questions. For now, I need to gather some more info and maybe some more tools and parts. Thanks, you guys are great. Link to comment Share on other sites More sharing options...
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