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Low Compression XR350R

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Got an odd problem on my XR350R  Recently bought it and previous owner said it had been sitting for a few years. It won't start. When I do a compression test I get around 30 psi after 12-15 kicks with the throttle wide open. This is with the auto decompression system connected. I disconnected  the decompression cable and after 12-15 kicks I get 0 psi. With or without the decompression system connected the effort to kick it over does not change. Where do I look from here?

Anyone experienced this same issue? Thanks for any advice.

 

 

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Got an odd problem on my XR350R  Recently bought it and previous owner said it had been sitting for a few years. It won't start. When I do a compression test I get around 30 psi after 12-15 kicks with the throttle wide open. This is with the auto decompression system connected. I disconnected  the decompression cable and after 12-15 kicks I get 0 psi. With or without the decompression system connected the effort to kick it over does not change. Where do I look from here?
Anyone experienced this same issue? Thanks for any advice.
 
 
Some of our xr250/400s when parked for long time have zero comp. Pull start with another bike fixed. Comp back to normal

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If it were my new toy i'd rotate the engine to TDC on the compression stroke and check to see if the valves are opening and closing before adjusting the valves. Remove the spark plug and install an adapter with hose allowing compressed air into the cylinder. Listening for escaping air at the muffler as well the intake at the air box any hissing sounds. Second step if hissing to listen after removing the dip stick for hissing into the crank case from stuck rings, burnt hole in the piston or a scored cylinder bore. Next remove the header pipe and carb or carbs as you didn't state the year of the bike having a single or dual carbs? Squirt  a little of oil wetting the valve seats from the port direction all four valves then pressure checking for air hissing at the valves. Also check the compression release connected to the right side exhaust valve checking that it is not holding the exhaust valve open or unseated. Add a couple squirts of oil from an oil gun into the cylinder then kick the engine over a couple times to wet the cylinder bore and rings. Retest to see if it's rings, valves or both that are leaking and hope you do not have a hole in the piston or that it had dropped a valve causing a lot of expensive replacement parts with internal damage. Head, piston and cylinder FUBARED from dropping a valve or possibly a valve stuck open. Had to mention owning a cheap endoscope and computer allowing you to look inside the engine through the spark plug hole will give you an idea of the engine's mechanical health. Hope it's not a rusted mess internally as rebuilding it is not cheap not alone locating parts. As mentioned what year, thinking a 83 to 85 bike? What's the overall condition as well how complete is it? It worth saving? How much money it cost you to buy it? "Yup she ran great the last time I ran it the seller's usual story", that's a big buyer's beware, it's very easy to get hosed on a purchase like this. Your emotions will empty your wallet. Trust me I got hosed on a super clean 85 XL350R of 2,900 original miles that ran silently mechanically also very hard to start. PO ran it in the dirt without an air filter by some untold miles hence a loss of 44 psi below spec. It was a sluggish dog. Hard to find parts, expensive as well beat to death worn out parts on Ebay if your lucky at new prices. Scrap parts at best so be careful not getting into a deep money pit project. ......~~=o&o>.......   

 

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Thumperhead.....thanks for the great response and suggestions.  A buddy dropped off a cylinder test kit today so I will try that test in the morning. The compression release looks to be working fine as far as I can see. I knew the guy I bought it from so I figured he would be straight with me.  Another buddy that knows the guy I purchased the bike from told me he saw it running in his driveway 2 years ago so I don't think this is anything major. I do have a scope but mine seems to be too big to get inside the spark plug hole. The bike is in pretty good condition. I have had both sides of the motor off and it is pretty clean inside. I should have mentioned the model. I could not find anywhere to ask XL questions so I posted my question here. It is a dual carb 1985 XL350R.  I will post the results after I do a few more tests tomorrow. Thanks for your help. 

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On 10/2/2019 at 8:40 AM, bajatrailrider said:
On 10/1/2019 at 5:37 PM, pelee said:
Got an odd problem on my XR350R  Recently bought it and previous owner said it had been sitting for a few years. It won't start. When I do a compression test I get around 30 psi after 12-15 kicks with the throttle wide open. This is with the auto decompression system connected. I disconnected  the decompression cable and after 12-15 kicks I get 0 psi. With or without the decompression system connected the effort to kick it over does not change. Where do I look from here?
Anyone experienced this same issue? Thanks for any advice.
 
 

Read more  

Some of our xr250/400s when parked for long time have zero comp. Pull start with another bike fixed. Comp back to normal

Bajatrailrider.....Thanks for the suggestion. I will give it a try. 

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pelee, so it's a 85 XL350R in your last posting above instead of an XR350 in your first post? That would be the dual carb engine which several people on this forum complained about vs tuning a single carb  engine. Starting in 83 to 84 XR's were dual carbed, 85 single carb as well dry sump vs 83 to 84 wet sump. The 83 to 85 XL's all dual carbed wet sump. Instead of drilling a bunch of holes destroying the XL's air box for more airflow why not remove the XL snorkel and install the larger XR snorkel? Requiring opening up the air box hole before installing looking factory original. Purchase a XL350R Honda Shop Manual ( yourBible) as your guide plus common sense these dual carb engines are not a mystery to properly adjust and tune. The rewards are great, I prefer the dual carb vs single carb. Use caution when removing the twin rubber intake tubes which are mounted to the airbox and carbs at the other end. The rubber is old and brittle, use a heat gun to soften before removing them from the carbs. Worse yet treat the head to carbs aluminum plate having two short rubber tubes the carbs mount into. Again a heat gun to soften the rubber before removing the carbs from the carb isolators. Better yet remove the isolator with carbs as a unit separating the carbs later. It is almost impossible finding a good used replacement not alone new isolator. One Ebay listing wanting $399 I recall for NOS isolators, he must of purchased a bunch of them then sticking it to desperate buyers in need on Ebay.  Another rare item finding the right side cover for the battery, lefts can be found but not rights. Took me 2 years to locate a good used one on Ebay. Besides the 84 twin carb XR350 engine I also picked up a XR compression release lever with cable, converting the kick start activated compression release to lever. I flat hate the XL's type of compression release.  Been told the crank triggering sensor can fail being it lives inside the engine with all the heat, not much said about the CDI unit as a failing item. You have all the plastics? Again Ebay  best source for used plastics, not cheap being 34 years old. Due to age, unknown condition I replaced all the wheel bearings, steering head as well the swing arm link bearings. Swing arm bearings still like new, hell it's only a 2,900 mile bike.  The lighted endoscope I have the head is just over 1/4" diameter hence able to look inside the cylinder. Be very careful separating the two carbs as there is a square casting that gets broken off twisting the carbs if the screws have not been removed first. Common mistaske. I prefer to remove the between carbs linkage at the throttle shafts vs popping off the plastic ball links as carb parts are about impossible to replace. Got lucky on Ebay again purchasing a like new pair of 84 XR350 carbs for the XL engine which i'll install the XR head with carbs. XR carbs have non smog larger jetting as well multi grooved slide needles vs single grooved XL slide needles and smaller leaner jetting to meet EPA restrictions. The XL's run too lean from day one not alone running oxygenated gas increasing leanness to the point of destroying the engine given time with excessive operating temps. Adjustable XR needles and richer jetting plus larger venturi area carbs, larger head intake runners of the XR head should wake up the XL engine. XR muffler also flows much better then the restrictive XL muffler. Money invested I should own a XL600 instead, emotions got me again.......~~=o&o>.......  

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On 10/8/2019 at 5:00 AM, ThumperHead said:

pelee, so it's a 85 XL350R in your last posting above instead of an XR350 in your first post? That would be the dual carb engine which several people on this forum complained about vs tuning a single carb  engine. Starting in 83 to 84 XR's were dual carbed, 85 single carb as well dry sump vs 83 to 84 wet sump. The 83 to 85 XL's all dual carbed wet sump. Instead of drilling a bunch of holes destroying the XL's air box for more airflow why not remove the XL snorkel and install the larger XR snorkel? Requiring opening up the air box hole before installing looking factory original. Purchase a XL350R Honda Shop Manual ( yourBible) as your guide plus common sense these dual carb engines are not a mystery to properly adjust and tune. The rewards are great, I prefer the dual carb vs single carb. Use caution when removing the twin rubber intake tubes which are mounted to the airbox and carbs at the other end. The rubber is old and brittle, use a heat gun to soften before removing them from the carbs. Worse yet treat the head to carbs aluminum plate having two short rubber tubes the carbs mount into. Again a heat gun to soften the rubber before removing the carbs from the carb isolators. Better yet remove the isolator with carbs as a unit separating the carbs later. It is almost impossible finding a good used replacement not alone new isolator. One Ebay listing wanting $399 I recall for NOS isolators, he must of purchased a bunch of them then sticking it to desperate buyers in need on Ebay.  Another rare item finding the right side cover for the battery, lefts can be found but not rights. Took me 2 years to locate a good used one on Ebay. Besides the 84 twin carb XR350 engine I also picked up a XR compression release lever with cable, converting the kick start activated compression release to lever. I flat hate the XL's type of compression release.  Been told the crank triggering sensor can fail being it lives inside the engine with all the heat, not much said about the CDI unit as a failing item. You have all the plastics? Again Ebay  best source for used plastics, not cheap being 34 years old. Due to age, unknown condition I replaced all the wheel bearings, steering head as well the swing arm link bearings. Swing arm bearings still like new, hell it's only a 2,900 mile bike.  The lighted endoscope I have the head is just over 1/4" diameter hence able to look inside the cylinder. Be very careful separating the two carbs as there is a square casting that gets broken off twisting the carbs if the screws have not been removed first. Common mistaske. I prefer to remove the between carbs linkage at the throttle shafts vs popping off the plastic ball links as carb parts are about impossible to replace. Got lucky on Ebay again purchasing a like new pair of 84 XR350 carbs for the XL engine which i'll install the XR head with carbs. XR carbs have non smog larger jetting as well multi grooved slide needles vs single grooved XL slide needles and smaller leaner jetting to meet EPA restrictions. The XL's run too lean from day one not alone running oxygenated gas increasing leanness to the point of destroying the engine given time with excessive operating temps. Adjustable XR needles and richer jetting plus larger venturi area carbs, larger head intake runners of the XR head should wake up the XL engine. XR muffler also flows much better then the restrictive XL muffler. Money invested I should own a XL600 instead, emotions got me again.......~~=o&o>.......  

Thumperhead.....did the cylinder leak test to find the left intake valve is leaking. So.....anything to try before biting the bullet and removing the head? Also......can valves be lapped if the problem is minor or is replacing the best way to go? Thanks a always for the advice.  

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With your findings of the left intake "leaking" i'd call it a stuck open valve as you have zero compression vs just a low reading compression test numbers. Dirty valve face and or seat be it rust which I believe is not the issue unless it's like the surface of an old nail buried in the ground for 15 years of crusty rust. With the valve cover off, engine at TDC what was the valve clearance on that "leaking" valve? If no clearance that means the valve is not seating hence the loss of compression. If a wide gap like 1 mm or 0.025" or greater it's a stuck open valve. How bad a the valve is stuck open plus how far open then you might be talking piston to valve impact causing a bent valve now not able to seat causing a zero compression issue. That would require removing the head which can be done with engine still in the frame but a PITA which can be done vs removing the engine. Full engine removal the easy way is to fully unbolt it but leave a couple long bolts in place, lay the bike on the ground over a big piece of carpet, remove those couple of bolts and lift the frame off the engine. Best easiest done with a bare frame vs or wheels removed making a light frame to lift vs the engine as it's a heavy lump. Back to the stuck open valve if that's the issue, apply penetrating oil in the intake port around the valve guide as well between the valve spring, keep applying for a couple days then with a brass drift or rod and a steel or brass (not plastic or rubber) bang on the rocker at the adjustment screw and nut area. Might get lucky unsticking the valve stem to guide. If the valve seated, back off the adjuster to confirm full seating by the spring and not held open by the cam . Your still only half way home as without seeing the valve face and seat area for condition like clean and not having surface rust as well possibly a bent valve then head removal would be required. BTW you checked the valve spring to see if it's not broken? With the smaller endoscope with light i'd also look at that intake valve pocket in the piston to see of contact had been made and how hard of impact as this would suspect a possibly bent valve. You never mentioned the mileage on this bike as that would cause concern about the condition of the timing chain and slipper if they are worn out, another item to check.  This bike stored in a shed not in the weather plus the carbs and air box installed preventing water from entering the engine? A Factory 83, 84 to 85 Honda Motorcycle Shop Manual would be your best investment if your without one to understand this bike and engine. I recall $35 plus $11 shipping my manual your best investment vs those known for wrong information Haynes or Clymer manuals sold at auto parts or bike shop manuals. 

I can not over emphasize how easy it is to damage the carbs (broken castings) as well the rubber intake to carbs especially the carbs to head rubber isolator due to the old hard and brittle rubber being damaged while taking things apart. Almost impossible items to locate not able to replace expensive good new or used 34 year old parts. There is a reason why several members on this forum had sold their 80's era XR's and XL's due to not finding parts and if so used junk parts costing more in the end vs a newer model bike overall. Love and emotions will empty your wallet everytime, bike wise not women.......~~=o&o>.......

Edited by ThumperHead

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On 10/9/2019 at 12:47 PM, ThumperHead said:

With your findings of the left intake "leaking" i'd call it a stuck open valve as you have zero compression vs just a low reading compression test numbers. Dirty valve face and or seat be it rust which I believe is not the issue unless it's like the surface of an old nail buried in the ground for 15 years of crusty rust. With the valve cover off, engine at TDC what was the valve clearance on that "leaking" valve? If no clearance that means the valve is not seating hence the loss of compression. If a wide gap like 1 mm or 0.025" or greater it's a stuck open valve. How bad a the valve is stuck open plus how far open then you might be talking piston to valve impact causing a bent valve now not able to seat causing a zero compression issue. That would require removing the head which can be done with engine still in the frame but a PITA which can be done vs removing the engine. Full engine removal the easy way is to fully unbolt it but leave a couple long bolts in place, lay the bike on the ground over a big piece of carpet, remove those couple of bolts and lift the frame off the engine. Best easiest done with a bare frame vs or wheels removed making a light frame to lift vs the engine as it's a heavy lump. Back to the stuck open valve if that's the issue, apply penetrating oil in the intake port around the valve guide as well between the valve spring, keep applying for a couple days then with a brass drift or rod and a steel or brass (not plastic or rubber) bang on the rocker at the adjustment screw and nut area. Might get lucky unsticking the valve stem to guide. If the valve seated, back off the adjuster to confirm full seating by the spring and not held open by the cam . Your still only half way home as without seeing the valve face and seat area for condition like clean and not having surface rust as well possibly a bent valve then head removal would be required. BTW you checked the valve spring to see if it's not broken? With the smaller endoscope with light i'd also look at that intake valve pocket in the piston to see of contact had been made and how hard of impact as this would suspect a possibly bent valve. You never mentioned the mileage on this bike as that would cause concern about the condition of the timing chain and slipper if they are worn out, another item to check.  This bike stored in a shed not in the weather plus the carbs and air box installed preventing water from entering the engine? A Factory 83, 84 to 85 Honda Motorcycle Shop Manual would be your best investment if your without one to understand this bike and engine. I recall $35 plus $11 shipping my manual your best investment vs those known for wrong information Haynes or Clymer manuals sold at auto parts or bike shop manuals. 

I can not over emphasize how easy it is to damage the carbs (broken castings) as well the rubber intake to carbs especially the carbs to head rubber isolator due to the old hard and brittle rubber being damaged while taking things apart. Almost impossible items to locate not able to replace expensive good new or used 34 year old parts. There is a reason why several members on this forum had sold their 80's era XR's and XL's due to not finding parts and if so used junk parts costing more in the end vs a newer model bike overall. Love and emotions will empty your wallet everytime, bike wise not women.......~~=o&o>.......

Hey Thumperhead....finally getting this sorted out. I removed the head. Left the motor in the frame. Not too difficult. Lapped the valves and reassembled the head. It looked pretty good. Put the head back on and snapped one of the small bolts on the cam cover.....one of the 118mm bolts. Removed the head again, removed the broken piece of bolt, and reassembled everything. A flat tracking buddy stopped by to have a look. He suggested we try to push started the bike. Fired up no problem. He suggested removing the decompression cable and now it seems easier to start. So.....looks like we are all good. Just need to wait for spring for some decent riding weather. Currently it's 40F. Not so nice. Thanks again for all the advice.

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3 hours ago, pelee said:

Hey Thumperhead....finally getting this sorted out. I removed the head. Left the motor in the frame. Not too difficult. Lapped the valves and reassembled the head. It looked pretty good. Put the head back on and snapped one of the small bolts on the cam cover.....one of the 118mm bolts. Removed the head again, removed the broken piece of bolt, and reassembled everything. A flat tracking buddy stopped by to have a look. He suggested we try to push started the bike. Fired up no problem. He suggested removing the decompression cable and now it seems easier to start. So.....looks like we are all good. Just need to wait for spring for some decent riding weather. Currently it's 40F. Not so nice. Thanks again for all the advice.

Dry roads 40*F is not cold dressed properly as well being excited to ride again. Even a 1/2 hour fun ride is'n't that cold. 

Your 85 XL350R is the exact same bike I have but it's in a million pieces and down to bare frame at present time. There were a lot more XR's sold than XL's hence more parts available.  Caution as a lot of XR's have had a hard life with parts about scrap metal value only. If I were you I would ditch that kick start activated compression release cable, seal off the case opening or install a XR side cover (no hole) then install a XR bar lever with cable to your XL head. Better yet get on the hunt for a XR head, XR carb and XR insulator. Make note, XL insulator to XL head only, XR insulator to XR head only, they are different at the sealing areas around the ports. Do not cross mix, massive air leak no run condition. With the XR head the intake port cross sectional area is 27% larger than the XL head., same valve diameters. Also the XR carbs at the vertical venturi wall area are slightly wider than the XL carbs hence increased fuel / air flow. Note, the XL's slide needle has only one groove, no altering the fuel ratio raising the needle unless washers installed under the needle retaining clip due to it being a smog regulated engine allowed on open road. The XR's needles have 5 groove needles allowing tuning the engine richer as well allowing it to run cooler than the already overly lean tune of XL engines. No smog regulations being off road bike. Heat the killer of these XL engines. Hell even add a XR 400 horse shoe shaped oil cooler mounted at the steering head of the frame looking nice and tucked out of sight vs aftermarket coolers frame mounted which work but look ugly.

Compression release cable completely removed from the lever on the head you should have a hard to kick over engine with full compression as well true compression numbers off a compression gauge, not the bleed down type of tester. Both come in handy depending on what your testing for at that moment.

Did you read a post by another ThumperTalk member that had pictures of the left side of the cam oiling holes drilled out slightly larger as well the feed pipe banjo bolt drilled out increasing oil flow to the almost dry running left half of the cam? The pocket below the cam lobes now having a small puddle of oil. Free easy modification preventing cam and follower failures. This would be a big improvement in the oiling of the cam followers being at the end of the line as they run on the verge of dry destroying cams, followers and heads. Big BOOM expensive damage that could of been prevented......~~=o&o>........ 

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